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 Cæsar 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.