Chapter 7 THE RISE OF ELECTRICITY, STEAM AND CHEMISTRY

The invention of the first electrical machine was made by Otto Von Guericke, of Magdeburg, about 1670. It consisted of a sulphur ball, a stick with a point, and a linen thread "an ell or more long," hanging from the stick. The lower end of the thread being made to hang "a thumb breadth distance" from some other body, and the sulphur ball rubbed and brought near the point of the stick, the lower end of the thread moved up to the body.

The ball being removed, the lower end of the thread would drop away from the body; so that by moving the ball back and forth, the lower end of the thread would be made to move back and forth simultaneously.

It may be objected that Guericke made no invention, because he did not conceive the idea of making a machine or instrument and did not, in fact, produce one: that he merely made a discovery. The author admits that such an objection would have great reasonableness, and that Guericke's feat is a little hard to class. It is classed by many as an invention, however, and the present author is inclined to class it so; because there seems no reason to doubt that Guericke first conceived the idea of doing what he did do, and that he did produce a device whereby an actual motion of a rubbed ball at one place caused actual motion at another place, through the medium of a current of electricity that traversed a conductor joining the two places. The device is sometimes spoken of as the first telegraph instrument.

Guericke (like Gilbert) was more distinctly an experimenter than an inventor,-and (like Gilbert) his work was not only in electricity, but in most of the other branches of science. Of the two, Guericke seems to have covered a wider field, and to have been more distinctly an inventor. His celebrated experiment of holding two hollow hemispheres together, then exhausting the air from the hollow sphere thus formed, and then demonstrating the force of the atmosphere by showing that sixteen horses could not pull the hemispheres apart, indicates just the kind of clear apprehension of the laws of Nature that characterizes the inventor.

By some, Guericke is esteemed the inventor of the first electric light, because by rubbing a sulphur ball in a dark room he produced a feeble electric illumination. Of Guericke's discoveries and inventions, the only one that has survived as a concrete apparatus is the air pump; but it is doubtful if the direct influence on history of the air pump, great as it has been, has actually been any greater than the indirect influence of his less widely known discoveries and experiments.

Hero's Engines

One of the early influences of the art of printing was to bring to the notice of some restless minds the writings of Hero and Archimedes. In Hero's Pneumatics, published more than 120 years before Christ, he gives such a clear account of an invention of his own, in which the expansive force of steam was used to give and maintain motion, as to establish thoroughly his right to the basic invention of the steam engine. He described three apparatus that he devised. In one, the currents of air and aqueous vapor rising through a tube from a hollow sphere, containing water, under which a fire is burning, support a ball placed immediately above the tube, and make it seem to dance. In another apparatus, a hollow sphere into which steam has arisen from what we now call a boiler, is supported on a horizontal or vertical axis, and provided with tubes that protrude from the sphere, and are bent at right angles to the radius and also to the pivot. The inner ends of these tubes lie within the sphere, so that the steam passes from the sphere through the tubes. As soon as this happens, the sphere takes up a rapid rotation, that continue so long as the steam continues to escape from the nozzles of the tubes, which point rearwardly. A third apparatus was merely an elaboration of the second, in that the sphere was connected with an altar which supported a large drum on which were figures representing human beings. The fire being lighted, the sphere would soon begin to revolve, and with it the drum; and the figures on it would seem to dance around, above the altar. The invention was probably to impress the people with the idea that the priests were exerting supernatural power.

Hero's Altar Engine

Hero's wonderful invention remained unused and unappreciated for nearly 2,000 years. About 1601, an Italian named Della Porta, published a book that seems to show acquaintance with it, also with the fact that if water be heated it is converted into a gas that can raise water to a height. In 1615, a Frenchman named de Caus published a book in which he showed a hollow sphere into which water could be introduced through an orifice that could then be closed; the sphere carrying a vertical tube that dipped into the water at its lower end, and ending in a small nozzle at its upper end. When a fire was started under the sphere, the air in the upper part expanded, and forced down the water that occupied the lower part, so that a jet of water would soon issue from the upper end of the tube. Of course, this was really less than Hero had done, because the appliance described did not constitute a machine, in any real sense of the word.

In 1629, an Italian named Branca carried Hero's invention a step further, by inventing a simple apparatus whereby the revolution of Hero's hollow sphere was communicated to a series of pestles in mortars, and put to the useful work of compounding drugs. Branca seems entitled to the basic invention of the steam engine as an industrial machine.

About 1663, the Marquis of Worcester invented a steam engine that exerted about two horse-power, and was employed to raise water from the Thames River, and supply it to the town of Vauxhall. Six years later (1669) Captain Thomas Savery erected a steam engine about twenty-five feet above the water in a mine, and successfully drew water out. This was a very important feat, because the difficulties surrounding the problem of freeing the mines from water were extremely great, and the desirability of overcoming them was equally so. In Savery's engine, there were two boilers in which steam was raised, and two receivers communicating with them. Steam being admitted to one receiver, the connection with the boiler was shut off by a valve, and a cold jet was then suddenly thrown on the receiver, condensing the steam and forming a partial vacuum. This vacuum the water below immediately rushed up to overcome. Connection with the pipe leading down was then shut off, and steam introduced to the receiver. This steam forced out the water from the receiver into a pipe, which discharged it above. This operation was then performed by the other boiler and receiver; so that, by their continued and alternate action, a fairly continuous stream of discharged water was maintained.

This invention was quickly followed by Captain Savery with another, by means of which the discharge stream was made to fall on a mill-wheel, as though from a natural waterfall. Several of these machines were erected for actuating the machinery of mills and factories in the district.

In 1690, Dr. Papin invented a steam engine, in which he used a cylinder containing water, with a piston so arranged that, when the water was heated, the steam would raise the piston. The fire being then removed the pressure of the atmosphere would force down the piston. This was followed shortly by an invention of Newcomer and Cawley, which was a very considerable advance on previous engines. It comprised a separate boiler and furnace, a separate cylinder and piston, means for condensing the steam in the cylinder by injecting water into it, and a system of self-acting valves that were opened and closed by a long beam that was moved by the piston. Furthermore, this beam communicated motion to a pump that pumped the water up directly. This engine was so efficient and so practically useful, that it was very generally introduced into service for draining mines throughout England. About 1775, Smeaton built an engine carefully designed on these lines, of which the cylinder was 72 inches in diameter, and the length of stroke was 10 feet and 6 inches.

In 1725, Jacob Leupold invented an engine, in which the work was done by steam alone, instead of by the atmosphere, as in the engines that immediately preceded it. Leupold used two cylinders. They were open at the top to the atmosphere as in the others, but he used higher pressures of steam, and arranged a four-way cock between the bottoms of the two cylinders in such a way that the bottom of each cylinder, in its turn, was connected to the boiler or to the open air. Each cylinder actuated directly a separate vibrating beam, which in turn actuated the piston of a pump; the two pistons acting reciprocally, each drawing up water in its turn.

Leupold's Engine

In 1765, James Watt made the very great improvement of providing a condenser separate from the cylinder of the engine, so that the great loss of heat caused by cooling the cylinder and then heating it at each stroke was wholly avoided. He covered the cylinder entirely, and surrounded it with an external cylinder kept always full of steam, that maintained the cylinder at a high temperature. The steam, instead of being condensed within the cylinder, after it had done its work, was allowed to escape into the condenser. To facilitate this action, the condenser was fitted with an air-pump that maintained a good vacuum in it.

In 1769, Watt invented an improvement that consisted mainly of means whereby the supply of steam to the cylinder could be shut off at any desired part of the stroke, and the steam allowed to complete the rest of the stroke by virtue of its expansive force. This invention increased tremendously the efficiency of the engine: that is, the amount of work done with a given amount of steam.

During all this time, Watt had realized that virtually all the work was done on the down stroke, and none on the up stroke, and also realized that it would be highly desirable to devise an apparatus whereby the reciprocating motion of the piston could be converted into a rotary motion. Watt was able to accomplish both feats, and to connect the bottom and top of the cylinder alternately with the condenser and boiler by a simple mechanism driven by a wheel rotated by the engine. The result was the reciprocating steam engine in its main features, as it exists today.

The influence of Hero's invention on history is not direct, because his engine has never been employed for any industrial purpose. But Hero's engine has had an enormous influence on history, nevertheless, because it supplied the basis on which the steam engine of the last two centuries has rested. The influence of Hero's invention was not realized until two thousand years after he had died, and until after all those men had died whose names have just been mentioned. It is inconceivable that any of those men could really have expected that their work was to have even a small fraction of the influence on mankind that it actually has had. The influence of Watt's work became visible to some degree before he died, and became clearly visible not very long after he had died; so clearly visible that by many men Watt is credited with the invention of the steam engine. But his good work was built on the good work of his predecessors, whose main work was in making Watt's work possible. The successive feats of all, like the successive layers in the foundations of any building, were to support, in time, the whole superstructure of the great and beneficent science of steam engineering.

But the work done by these men was not all the work that had to be done, to make Watt's steam engine the efficient machine it was. These men were the men who are directly to be credited, but they were not the only men engaged. Neither did they belong to the only class of men engaged. There was another class of men whose labors were equally arduous, and equally important, though not so clearly in evidence-the physicists, as we now call them. It was by the knowledge which they gleaned regarding the properties of steam and air and water and iron, regarding the laws of motion and heat and work and force and weight and mass, that the inventors' experiments were guided. It is true that the science of physics was then in its infancy, as we realize with the knowledge of the science today; but Aristotle in the days of Greece, and Archimedes and Hero later, and Galileo and many others in Italy-as well as Guericke in Germany, Newton and Gilbert in England, and others of less note, had evolved a good deal of order out of what had been chaos, and had given inventors a great deal of firm ground on which to stand themselves and raise their structures. And reciprocally, the inventors found themselves confronted with problems of a kind that gave opportunities for the physicists to show their skill and knowledge.

Thus were opened up promising avenues of investigation, and not only of investigation, but of invention also. For it is obvious that, while investigation and experimentation can hardly fail to secure data, they may secure nothing else, and usually do. But mere data are mere facts; and, valuable as they are if suitably classified, they are not valuable unless they are classified; and even after data are classified, they are not useful until some use is found for them. The data in card-indexes are mere unrelated facts, and are almost useless, until they have been classified and arranged in boxes alphabetically labeled. Then they are useful whenever any use is found; when, for instance, some one is seeking information on a certain subject. In this condition, data are like material substances, in that they are available for use,-in fact, data are often spoken of by writers as "material"; a certain series of incidents, for instance, supply "material" for a story. Now, just as pieces of iron and brass supply material with which an inventor can create a new machine, so classified facts, or data, supply material with which an inventive investigator can create a new theory, or formulate a new law.

Our books on physics are full of accounts of experiments and investigations conducted by such men as Hero, Archimedes, Gilbert, Galileo and many others, the consequent discoveries that they made, and the consequent laws that they enunciated; but those books could not possibly describe all the investigations that have ever been made. Those which they describe are those that ended in some definite creations, such as the hydrostatic law enunciated by Archimedes. Most investigations, experiments and researches have ended in nothing definite:-most of them, in all probability, have not even established facts. The investigations that we studied about when boys were such as those of Archimedes, that presented us with inventions, in the form of useful and usable laws. No appreciable difference is apparent between the mental operations of Archimedes in inventing these laws and his mental operations in inventing his screw: for in both cases the mental operations consisted mainly in conceiving an idea and then embodying it. The Archimedean screw was a machine of an entirely new kind that, in the hands of a man understanding its use, would enable the man to do something he could not do before-or enable him to do a thing he could do before, but do it better. So were his laws. The laws have been utilized ever since, as definite and concrete devices; and to a much greater extent than the special form of screw that he invented.

In a like way, all the laws that investigators have put into concrete and usable form, have been used by other investigators as bases for further investigations, and by inventors as bases for future inventions. Even the inventor of the fist-hammer had to know something about the material which he employed; he had to know that it was hard and heavy, for instance, and that it could be hammered so as to have a point and a sharp edge. He had to know also something about the flesh of a man: he had to know that if his flesh was struck with a sharp hard instrument, it would be bruised, and the man injured, and maybe killed. Similarly, the inventor of the gun, and the inventor of printing, and the inventors of steam engines, had to know a good deal about the materials which they employed, and about the uses to which their appliances could be put. Naturally, they had to know much more than did the inventor of the fist-hammer. But the inventor of today has to know still more, because there is still more to know. An inventor of the present day who knew no more about physical science than Galileo did would not be able to go far.

A like remark may be made about any man in any vocation, as compared with his predecessor in Galileo's time. The machine of civilization is so vast and so complex, that the amount of knowledge which anyone of us needs in mere daily life is almost incredible. Let anyone try to enumerate all the facts he knows! The attempt will convince him quickly.

It may be pointed out here that, while modern civilization differs from ancient civilization in many ways, it differs more in complexity than in any other one way. Some of the factors of ancient civilization were as good as those of today; such things, for instance as temples and pyramids and stationary objects in general. But the ancients did not understand motion clearly, especially irregular motion; and they had no fast vehicles of any kind. Their knowledge of statics must have been fairly complete, or they could not have built their temples and pyramids; but their records show little understanding of dynamics.

Now the basis of dynamics is mathematics. Dynamics is the result of the application of mathematics to the observed effects of force on bodies, in producing motion. Dynamics is a branch of the science of mechanics, and a most difficult branch. It is built on the observations, calculations and conclusions of Newton and a host of experimenters and mathematicians of lesser mentality, and it could not have come into being without them.

But dynamics has not been the only physical science involved in making the machine of civilization. All the physical sciences have taken part; and each one has taken a part which was essential to the final result, and without which the final result could not have been attained. The science of light made possible the solution of our problems of illumination and the development of inventions for producing it; the science of acoustics made possible the solution of our problems of sound, including music, and the invention of acoustic and musical instruments; the science of heat made possible the invention of all the complex and powerful steam and gas engines that have revolutionized society; the science of electricity (including magnetism) has made possible the invention of those electric and electro-magnetic machines that have supplemented the work of the steam engine; and the science of pneumatics has made possible the invention of those "flying machines" of many kinds, that promise to complicate civilization further still.

But let us realize clearly that no one of these sciences by itself has been able to perform any of the feats just mentioned. Each one was virtually dependent on every other one; and all were dependent on mathematics. In order to make the steam engine work efficiently, it was not enough that heat should expand water into steam: the mathematical laws which showed how much water was needed to secure a certain amount of steam, for instance, and how a certain desired pressure of steam could be secured, had first to be comprehended and then to be followed. In order to have boilers and engines so designed as to prevent disastrous explosions, the laws governing the strength of materials had to be known and followed. In order that a projectile could be so fired from a gun as to reach a certain predetermined spot, the laws of heat, pneumatics, chemistry and dynamics had all to be understood and followed with exactness.

But it was not only the machines and instruments that needed the assistance of those sciences, it was the sciences themselves; because it was only after eliminating phenomena caused by one agency from those caused by another, that accuracy in any conclusions whatever could be secured; and in order that the phenomena caused by one agency could be kept separate from the phenomena caused by another agency, the laws underlying both had to be understood. The science of light could not be developed until the action of heat was fairly well understood; dynamics had to wait on statics; Newton could not have contributed what he did to astronomy, unless the science of light (including optics) was sufficiently understood; and the laws of pneumatics could not have been developed, unless the laws of heat had been developed, etc. And not one of the physical sciences could have gone beyond the state of infancy, if the science of mathematics had not been invented and made into a workable machine.

The paragraph above may be put into a different form, and made to state that all the physical sciences have been brought up to their present stage, by subjecting the phenomena studied by each science to quantitative investigation. It was by making these quantitative investigations that Newton and the others were able to ascertain the exact facts from which to start in their endeavor to discover the laws of nature; and it was from the laws of nature thus induced that later investigators were able to start on still further expeditions of discovery into the unknown. As the common basis of all quantitative work is mathematics, the common basis of all the physical sciences is mathematics. This makes all the physical sciences interdependent, despite the fact that each is independent of the others. Each one of the physical sciences has contributed its part to building the machine of civilization; the part that each has specially contributed can be clearly specified; and yet, since the machine is the result of the combination of what all have contributed, their contributions are interdependent. This remark applies to the various parts of all machines. The piston of a steam engine, for instance, and the valve that admits steam to the cylinder are entirely separate from each other; but from the mere fact that they both work together, each one must be designed and operated with reference to the other; so that both in their construction and their operation, they are interdependent.

Francis Bacon, in the sixteenth century, may be said to have inaugurated the system on which the whole of modern progress has been based, and Newton in the seventeenth century to have taken up Bacon's work and carried it further on. Following Newton, only a few great investigators can be seen in the seventeenth century; but in the eighteenth, began that intense and brilliant movement of investigation, discovery and invention, that has been adding more and more to the machine of civilization-and still is adding more.

One of the earliest and most important contributions was an apparatus for measuring time accurately. Who was the inventor is not precisely known. It seems fairly well established, however, that Galileo was the first to call attention to the fact that the vibrations of a pendulum were nearly isochronous, and could be used to measure the lapse of time; and that Galileo's son (as well as Dr. Hooke, Huygens and a London mechanic named Harris, in the early part of the seventeenth century) made clocks based on that principle. It is fairly well established also that Huygens was the first one to make a mathematical investigation of the properties of the pendulum, and to enumerate the laws since utilized for making accurate clocks and watches.

Most of the investigators of the eighteenth century occupied themselves with studies indirectly or directly caused by the invention of the steam engine, that is with studies relating to heat and light; but, by reason of the interdependence of all the physical sciences, their investigations led them automatically into the allied fields of acoustics and electricity. Their investigations led even further; they led to the establishment, on the ruins of the illusions of alchemy, of a wholly new and supremely important science, chemistry.

One of the most important inventions of a purely scientific character made during the period was one that has never been known by any other name than "Atwood's machine." It is an interesting illustration of the addition of invention to investigation, in that its end was-merely investigation; and it reminds us of a fact that many people are prone to forget, that invention may be applied to almost any purpose whatever, and that even a "machine" may be devoted to a purpose not utilitarian.

Atwood's machine was the outcome of studies into the relations between force and a body to which force may be applied. Galileo had shown that a body subjected to a constant force, like that of gravity, will gradually acquire a velocity and at a constant rate; and also that this rate, or acceleration, is proportional to the force (leaving out the effect of air resistance). Atwood's machine consisted merely of an upright with a pulley at its upper end over which passed a cord, to both ends of which weights could be attached. In any given experiment, a weight was attached to one end and allowed to fall free; but another weight could automatically be attached to the other end by a simple device, when the first weight had fallen through any predetermined distance. If the added weight were equal to the first weight, the velocity of movement became uniform at once; while if it were less, the velocity approached uniformity to a degree depending on the approach to equality of the two weights. While this machine did not establish any new law, or prove anything that Newton had not proved before, it supplied a very valuable device for conducting quantitative experiments with actual weights, and for instructing students.

The first important improvement in the art of printing was made by a Scotch goldsmith named William Ged, about the year 1725. It is now called stereotyping, and it seems to have been successful from the first, from a technical point of view. It was far from successful from a financial point of view, however, mainly because of the opposition from the type-founders; so that Ged died without realizing that he had accomplished anything. Ged's invention was not put to practical use for nearly fifty years after his death; but after that, its employment extended rapidly over the civilized world. Ged's experience was bitter, but no more so than that of many other discoverers, inventors and benefactors. He did not profit in the least by his invention; in fact, it must have brought him little but exasperation and discouragement. But can we even imagine civilization to exist as it exists today, if stereotyping had not been invented?

An invention of a highly original kind was made some time in the middle of this century which is attributed by some to Daniel Bernoulli, one of the eight extraordinary investigators and scholars of that family. According to this theory, the pressure of any gas is due to the impact of its molecules against the walls of the vessel containing it. Naturally, the greater the density of the gas, and the greater the velocity of the molecules, the greater is the pressure. This theory has greatly assisted the study of gases, and contributed to the investigation of electric discharges in gases and partial vacua, and therefore to the modern science of radio-activity.

In the year 1640 there came to the little throne of the Margravate of Brandenburg a coarse and violent man, who conceived a principle of government that seems to have been wholly novel at that time, the principle of efficiency. Having conceived this idea clearly in his mind, he proceeded to develop it into a system of administration, in spite of opposition of all kinds, especially inertia. He ruled till 1688. He found Brandenburg unimportant, disordered and poor; he left Brandenburg comparatively rich, with a good army, an excellent corps of administrators, a very efficient government, and a recognized standing before the world. For his contribution to the cause of good government, he is known in history as The Great Elector. He might be called, with much reasonableness, the inventor of governmental efficiency, if Julius C?sar had not in some degree forestalled him.

He was followed by his son, who contributed nothing to this cause or to any other, but who was able to take advantage of his father's work and be crowned as King of Prussia. He was followed by his son, King Frederick William I, who was a man like the Great Elector, his grandfather, in the essential points of character, both good and bad.

He was somewhat like Philip of Macedon also; for he conceived the idea of making his army according to a certain pattern, novel at that time, though considerably like the pattern that Philip had employed. The likeness was in so organizing and training the soldiers that a regiment or division could be handled like a coherent and even rigid thing, directed accurately and quickly at a pre-determined point, and made to hit an enemy at that point with a force somewhat like the blow of an enormous club. He succeeded during his reign of twenty-seven years in developing his conception into such a perfect and concrete reality, that he was able on his death in 1740 to bequeath to his son a veritable military machine-the first since the days of Rome.

These two Frederick Williams were inventors in the broad sense of the word, and made inventions that have had an influence on history since they died, as great as that of almost any other contemporary inventions that can be specified. Their immediate influence was to make it possible for the son of King Frederick William, Frederick the Great, to put Prussia in the first rank among the nations, and to lay the foundations of the German Empire.

It may be objected that the ultimate result was not extremely great, after all, because the German Empire fell in 1918. To this possible objection, it may be answered that, nevertheless, the doings of Prussia and the German Empire have had an enormous influence up to the present time; and that, though the empire itself has ceased, the influence of its policies and doctrines, of its military system, and, above all, of its doctrine of efficiency in government has not ceased, and shows no signs of ceasing. Besides, history still is young.

Frederick the Great made no inventions in improving the military machine bequeathed him; but he did operate it with inventiveness, daring and success. He showed these qualities in his actual operations in the field; but he showed inventiveness in an equal degree before those operations took place, in the plans which he prepared. As a tactician, Frederick could hardly help being good, in view of the training he had received and the military atmosphere in which he had been born and bred. But no amount of training could have given Frederick the brilliant and yet correct imagination that enabled him to see entire situations clearly and accurately with his mental eye; that enabled him to form a correct picture of the mission in each case, the difficulties in the way of accomplishing it, and the facilities available for his use. And, equally, no amount of training or knowledge or experience could of themselves have given him the constructive ability necessary to build up such plans as he built up, for accomplishing the mission with the facilities available and in spite of the difficulties.

Frederick's first invention was his successful invasion of Silesia. This may be called by some "an invention of the devil," and perhaps it was inspired by him. But even if Frederick's conception came straight from the devil, it was a brilliant conception, nevertheless, as the conceptions of the devil himself are popularly supposed to be. So original in conception and so perfect in development was Frederick's invented plan, that he had seized the capital of Silesia before Austria had taken any real defensive measures of any kind.

During the first half of Frederick's reign, or twenty-three years (from 1740 to 1763), he was engaged continually in war or preparation for war; and in both activities he had to plan to fight against odds that often seemed overwhelming. They would have overwhelmed any man, except a man like Frederick. It is true that Frederick had two advantages, the best trained army, and the fact that all his forces, military and political, were united under one head-his own. But it is the verdict of history that even these advantages were far from sufficient to explain his victories; that his victories cannot be explained except on the ground that Frederick showed a generalship superior to that of his foes. In what did its superiority consist? A careful study of his campaigns, even if it be not in detail, shows that Frederick was able to invent better plans than his adversaries, to invent them more quickly, and to carry them into effect more promptly. If he had been born under other stars, he might have exercised his inventiveness in such ways as men like Guericke, for instance, did; as is shown by his gathering around him, in the peaceful period of the latter half of his reign, a company selected from the most eminent philosophers and scientists of the age; and as is shown with equal clearness by his admirably conceived and executed measures for the better government of his country.

The middle of the eighteenth century is especially distinguished by the success of some extraordinary and brilliant experiments with electrical apparatus. One of the most important in results occurred about 1746, in the town of Leyden, where Muschenbroek invented a device that made possible the accumulating and preserving of charges of electricity. This appliance consisted of merely a glass jar, coated on the outside and the inside with tin foil. It was a most important invention, and it is still in general use, and called the Leyden jar.

The Leyden jar was soon put to practical work in electrical investigations, notably by the Royal Society in London; and many valuable demonstrations were made with it. Among these were the firing of gunpowder by the electric spark that passed when both surfaces of tin foil were connected by an external conductor; and the transfer of the spark over a distance of two miles, by using one discharging conductor or wire two miles long, the earth acting as the return conductor.

But the greatest results came from the investigations of Benjamin Franklin, who proved that there was only one kind of electricity, that the two coatings of tin foil were both charged with it, that one had more than its ordinary quantity, while the other had less, and that the spark was caused by the transfer of electricity from one coating to the other. These discoveries were as much as any one discoverer might reasonably be expected to contribute; but Franklin soon followed them by his discovery of the power of points to collect and discharge electricity. He then pointed out with extraordinary clearness the fact that all the phenomena which had been produced by electricity were like those produced by lightning; and made the suggestion that lightning and electricity were identical.

This was an interesting suggestion, but a suggestion only. To make it into a theory, or prove it as a law, an invention was required. Franklin made the invention. He conceived the idea of bringing down the electricity, with which he imagined that a storm-cloud was charged, by means of a long conductor, and of drawing off a spark from the lower end of the conductor as from an electrical machine. The long conductor he had in mind was a high spire that was about to be erected in Philadelphia. The erection of the spire being delayed, his imagination presented to his mind the picture of a kite flying near the cloud, and the charge flowing down the cord, made into a conductor by the accompanying rain. Forthwith, he embodied his conception in definite form by preparing a kite to which was connected a long cord, that ended with a piece of non-conducting silk, that was to be held in the hand, and kept dry if possible, and a key that was secured to the junction of the conducting cord and the non-conducting silk. The expectation was that the key would receive the charge from the cloud and give it out as a spark, if Franklin applied to it the knuckle of his disengaged hand. The invention was a perfect success in every way; sparks were given off, a Leyden jar was charged, and subsequent discharges of the Leyden jar were made to perform the same electrical feats as jars charged from ordinary electrical machines. (June, 1752.)

The courage shown by Franklin in performing this experiment may here be pointed out. To the eye of a casual observer, he must have been trying to get struck by lightning.

This brilliant invention caused Franklin to conceive another brilliant invention, the utilization of the discovery he had just made in combination with his previous discovery of the power of points to collect electricity. He embodied his conception in what we now call "lightning rods," by erecting on the highest points of houses thin metal rods or conductors, the lower ends of which were buried in the earth, while their upper ends were sharpened to points, and made to project upward, above the houses. Franklin's theory was that the points would collect the electricity from the clouds and allow it to pass harmlessly through the conductors into the ground. The invention worked perfectly, and has been utilized everywhere ever since.

Naturally, Franklin's epochal discoveries stirred the scientific world in Europe, and gave a great impetus to the study of electricity and the other physical sciences. One of the earliest important discoveries that followed (made by Mr. Cavendish) was that the electrical spark could decompose water and atmospheric air, and make water by exploding mixtures of oxygen and hydrogen. An epochal discovery was made by Mr. Cavendish about 1787, when he exploded a mixture of oxygen and nitrogen and obtained nitric acid.

In 1790 Galvani discovered that, if two dissimilar metals were placed in contact at one end of each, and if the free ends are put into contact with the main nerve of a frog's hind leg and the thigh muscle respectively, spasmodic muscular movements would ensue. In investigating the cause of this phenomenon, Volta discovered that if the lower ends of two dissimilar metals were immersed in a liquid they would assume opposite electrical states; so that if their outer ends were joined by a conducting wire, electricity would pass along it. This led him at once to the invention of the Voltaic cell. The enormous value of the Voltaic cell in building up the science of electricity need hardly be pointed out. It is still used in electric telegraphy as a source of current.

During the eighteenth century, the relations between chemistry and heat were very ill defined; but they were cleared up gradually by the researches of such men as Black in Scotland, Priestley and Cavendish in England, and Lavoisier in France. Black's work was mainly in making investigations of the phenomena of heat. In the course of them he discovered the important fact that different substances require different amounts of heat to be applied to a given mass to raise its temperature 1°. From this discovery arose the science of calorimetry, which deals with the specific heats of all substances, solid, liquid and gaseous, and which is necessary to the present science of heat and the arts that depend upon it. About 1774 Dr. Priestley discovered oxygen.

Lavoisier prosecuted rigorous researches in heat and chemistry, and finally made a discovery that cleared up a great fog of doubt as to the nature of oxidation, by proving that it consisted in an actual attack on a metal by oxygen, and that the increased weight resulting from oxidation was that of the oxygen that became associated with the metal in the form of rust. He therefore disproved the theory formerly loosely held that the increase in weight was due to the escape of a spirituous substance which the chemists of that day imagined to depart from the metal, and called by the name phlogiston. An analogous and equally valuable contribution by Lavoisier was that of introducing the use of exact measurements into the study of chemistry. The result of his labors was to put the science of chemistry on a new basis and to separate it from physics entirely.

It might be supposed that Lavoisier would live and die in great honor. He lived in comparative obscurity, and was publicly guillotined on a false accusation. He requested a brief respite, in order to complete an important experiment, and was told in answer that "the Republic has no need of philosophers." This was France's reward for one of the most useful lives that has ever been lived.

One of the most important industrial inventions ever produced and one of the first of the long list of inventions for making things by machinery that had formerly been made by hand, was the spinning machine, that was invented by Dr. Paul in England about 1738. Spinning is an exceedingly ancient art, and consists in forming continuous lengths of thread by drawing out and twisting together filaments of such material as wool, cotton, flax, etc. This art was practiced in many of the ancient countries; and it seems to have been practiced in essentially the same way in England in the eighteenth century A. D., as in Egypt and Assyria long before the eighteenth century B. C. About 1738 Dr. Lewis Paul invented and patented a simple mechanism that anyone with imagination could have invented at any time during the two or three thousand years before, in which the filaments were drawn between rollers. The invention seems to have been moderately successful from the start; for it is stated that in 1742 a spinning mill was in operation in Birmingham in which ten girls were employed, and in which the motive power was supplied by two asses. Paul's invention was improved by a weaver named Hargreaves, who invented the "spinning Jenny"; and it was later brought to a high state of efficiency and value by an invention of a poor and wholly uneducated barber, named Richard Arkwright. The spinning machines of the present day are of the highest order of intricacy, efficiency and usefulness; but they are all based directly on the invention of Arkwright, and his was based on the previous inventions of Paul and Hargreaves. Few persons have contributed so much as these three men of humble station to the comfort and well-being of the race.

On July 3, 1775, George Washington arrived at Cambridge, near Boston, and took command of an army of about 17,000 men that faced a British army occupying Boston. Washington devoted his energies to organizing and training his motley force during the ensuing fall and winter, the enemy making no decided move to drive him off. Finally, on March 4, 1776, having conceived a plan that promised success to him, he suddenly seized and fortified Dorchester Heights, about two miles south of Boston, from which he could command the whole of Boston and the channel south of it, by means of guns which he had ordered, to be dragged through the snow from Ticonderoga. His plan worked perfectly; for the British General Howe, after a vain attempt to drive Washington away, evacuated Boston himself, and took his army to Halifax.

This was Washington's opening move in our War of the Revolution. It was the execution of a plan admirably conceived. There may seem little of originality or brilliancy in it to us now, looking at a map of Boston in the quiet and safety of a library, but there must have been a great deal of merit and originality in it; for it took a British major-general completely by surprise, and compelled him to evacuate an important stronghold with a precipitancy that must have been distinctly galling to British pride. Few neater feats of strategy can be found in military history.

Washington's next feat was in extricating his force from a distinctly perilous position in Brooklyn in front of a superior British force, retreating across the East River to New York, and landing near what is now called Fulton Street. This was on August 30, 1776. The next three months were spent in maneuvers that showed great clearness in conception and great energy in execution on Washington's part, and ended with his occupying Trenton, and Howe occupying New York with the bulk of his forces. Washington had only a little more than 4,000 men, while Howe had 30,000. Washington's troops were discouraged, half-ragged, underfed and untrained; Howe's were elated, well clad, well fed and thoroughly trained. Washington was in as dangerous a plight as can easily be imagined. He extricated himself by conceiving and carrying into execution the brilliant plan of crossing the Delaware River on Christmas night, forcing his way through floating ice, and falling on the amazed camp of the Hessians on the other side. His invention worked perfectly, and effected almost a complete reversal in the relative conditions of the opposing forces; for it put the British on the defensive, and made them withdraw all their forces from New Jersey.

Thenceforward, Washington, by the exercise of imagination, constructiveness and sheet force of will, fought a continual fight against forces that were superior in material and training, but inferior in mentality. Finally, in August, 1781, the crisis came. The British were occupying New York, and Washington was in front of it, threatening to attack it, but knowing that he could not do so with success. About August 14 he received a letter written in July by Admiral Comte de Grasse, then in the West Indies, saying that he would start with his fleet and a force of troops for Chesapeake Bay on August 13. Washington knew that the British General Cornwallis was entrenched at Yorktown, near the mouth of the Chesapeake, with a force considerably inferior to his own. He instantly proceeded to embody in action an idea that he had already conceived-that of leaving the vicinity of New York secretly, and marching with the utmost possible despatch to Yorktown, and calling on de Grasse to assist him to capture Yorktown, and if possible Cornwallis. No invention ever succeeded better. Its influence on history was to precipitate the collapse of the entire British program of hostilities, and cause the establishment of the United States.

The balloon was invented about 1783. Mr. Cavendish had found that hydrogen was about seven times lighter than air, and Dr. Black had forthwith delivered a lecture in which he pointed out that a thin light vessel inflated with hydrogen should be able to rise and float in the air. He conceived the idea of the balloon, but made no invention. The Italian philosopher, Cavallo, about 1782, inflated soap-bubbles with hydrogen gas, but went no further. The subject of making balloons filled with hydrogen was widely discussed; but the first balloon really to rise was the hot-air balloon invented by Joseph and Stephen Montgolfier. This balloon made a successful ascent on June 5, 1783, carrying the two brothers, flew about ten minutes, and alighted safe, after a trip of about a mile and a half. This was followed on August 27 by a flight of a balloon filled with hydrogen gas, the design of which was made by the physicist Charles, and the cost of which was met by a popular subscription. The flight was followed shortly by many others. The first employment of balloons in practical work was in making observations of the enemy by the French army in 1794.

An important invention for utilizing mechanical power in place of hand-power was the power-loom invented in 1785 by Edmund Cartwright. This was an invention of the most clean-cut kind, originating in the conception by the Rev. Dr. Cartwright of the possibility of doing much more weaving by mechanical power than by hand, then constructing the machine to accomplish it, and then accomplishing it. An interesting fact in the early development of looms for weaving was the determined and angry opposition of weavers to each improvement in succession.

Another invention also utilizing external power, made near the end of the eighteenth century, was the hydrostatic press. It consisted of a vertical cylinder, fitted with a piston prevented by suitable means from rising, except against great pressures; the piston resting on a liquid in the bottom of the cylinder, which was connected by a small pipe with a small pump, by which more liquid could be forced in. When the pump was operated the pressure per square inch on the piston of the pump was communicated to each square inch of the large piston in the press, and a force exerted equal to that pressure multiplied by the difference in area of the two pistons. This is the model on which hydraulic jacks and many other hydraulic mechanisms are constructed; and it has taken a prominent part in the development of the science of hydraulics ever since it was invented.

Because of the gradual recognition of the value of sea-commerce in the British Isles, and the fact that the stormy seas adjacent necessitated the construction of ships at once sturdy and yet capable of speed, much study and experimentation were carried on during the eighteenth century, especially in England. In these experiments, the invention by Archimedes of the hydrostatic principle of buoyancy supplied the starting-point, and gave an excellent illustration of the influence of invention on history: for from experiments and investigations on floating bodies carried on in England, based on the invention of Archimedes, and followed by others of English origin, sprang England's merchant marine and England's navy and England's domination over a quarter of the land on the surface of the earth.

The eighteenth century closed with the invention of two very important mechanisms that reinforced the power of the human hand with power drawn from external sources: these were the threshing machine and the cotton gin; the former invented by Andrew Meikle in 1788, and the latter by Eli Whitney in 1793. It would be hard to decide with knowledge as to which has had the greater influence in constructing the machine of civilization; but it is not at all hard to realize that the machine of civilization could not have attained its present stage without the assistance of both.

One of the last important inventions of the century was that of an art entirely new, as distinguished from inventions like the cotton gin, that merely increased the value of an art already in existence. This was the invention of lithography, or printing from stone, made by Alois Senefelder in 1796. The first thing printed by him was a piece of music. While this invention was more brilliant than those of Meikle and Whitney, it was hardly so important. Nevertheless, it was important in a high degree and made a valuable addition to civilization.

An invention of a kind different from either Whitney's or Senefelder's was made on October 15, 1793, by Napoleon Bonaparte. He was at that time a young and ill-clad captain of artillery, attending a Council of War in Toulon. An idea for driving out the English had been conceived and embodied in a complete plan by a celebrated engineer, and it had been approved by the Committee on Fortifications. The youthful and prestigeless captain opposed this plan with a vehemence and convincingness that came to be familiarly known a few years later, and proposed in place of it a plan that he had himself conceived and embodied in a concrete form. His plan consisted in the main merely in mounting some guns on a point of land that he designated, from which they could command the British war-ships in the harbor; and it was so much simpler and in every way better, that, despite his obscurity and youth, it was adopted, and he himself was charged with carrying it into operation. This he did; and with such constructive skill and energy, that the British ships were driven from the harbor and the entire vicinity, and without doing any damage to the town. The British soldiers, then unsupported, immediately withdrew.

What was the determining difference between Napoleon's plan and that of the great engineer? The idea conceived.