Indeed one of the most interesting chapters of history is the effort of man to let some one else or something else do his work for him, while he enjoyed his leisure, sitting in the sun or painting pictures on rocks, or training young wolves and little tigers to behave like peaceful domestic animals. Of course in the very olden days, it was always possible to enslave a weaker neighbour and force him to do the unpleasant tasks of life. One of the reasons why the Greeks and Romans, who were quite as intelligent as we are, failed to devise more interesting machinery, was to be found in the wide-spread existence of slavery. Why should a great mathematician waste his time upon wires and pulleys and cogs and fill the air with noise and smoke when he could go to the marketplace and buy all the slaves he needed at a very small expense? And during the middle-ages, although slavery had been abolished and only a mild form of serfdom survived, the guilds discouraged the idea of using machinery because they thought this would throw a large number of their brethren out of work. Besides, the Middle-Ages were not at all interested in producing large quantities of goods. Their tailors and butchers and carpenters worked for the immediate needs of the small community in which they lived and had no desire to compete with their neighbours, or to produce more than was strictly necessary. During the Renaissance, when the prejudices of the Church against scientific investigations could no longer be enforced as rigidly as before, a large number of men began to devote their lives to mathematics and astronomy and physics and chemistry. Two years before the beginning of the Thirty Years War, John Napier, a Scotchman, had published his little book which described the new invention of logarithms. During the war itself, Gottfried Leibnitz of Leipzig had perfected the system of infinitesimal calculus. Eight years before the peace of Westphalia, Newton, the great English natural philosopher, was born, and in that same year Galileo, the Italian astronomer, died. Meanwhile the Thirty Years War had destroyed the prosperity of central Europe and there was a sudden but very general interest in “alchemy,” the strange pseudo-science of the middle-ages by which people hoped to turn base metals into gold. This proved to be impossible but the alchemists in their laboratories stumbled upon many new ideas and greatly helped the work of the chemists who were their successors.