Invention: The Master-key to Progress

by Bradley A. Fiske

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.