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.