Possibly the greatest single impetus given to progress about the year 1800 was that given by Lavoisier shortly before, which started the science of chemistry on the glorious career it has since pursued. As a separate branch of science, chemistry then began, though it had been the subject of investigation for many centuries, beginning in Egypt and the other ancient countries of the East. In the Middle Ages, it was known in Europe by the name Alchemy. Originally, and in all the long ages of its infancy, the investigations of the experimenters were carried on mainly to discover new remedies in medicine, or to learn methods to transmute base metals into precious metals; though there was a considerable degree also of pursuit of knowledge for its own sake. As a result of the investigations, many startling facts were developed, and many discoveries were made; but, for the reason that the investigations were not conducted on the mathematical or quantitative lines that had led to so much success in developing physics, alchemy or chemistry did not rest on any sure basis, and therefore had no fixed place to start from. It was in the same vague status that some subjects of thoughtful speculation are in today, such as telepathy, which may (or may not) be put on a basis of fact some day, and started forward thence, as chemistry was started. What gave chemistry its basis was the methods introduced by Lavoisier who was a practiced physicist. He introduced the balance into the study of chemistry, and raised it instantly from a collection of speculations to an exact science, capable of progressing confidently and assuredly thereafter, instead of wandering in a maze. Lavoisier gave chemistry a mathematical basis to start from, and sure beacon lights to guide it; and though many changes in its theory have been made from time to time, they have been due only to increase of knowledge and not to departure from fundamental principles. Finding that a substance was not an element, but was a compound of two elements, or more than two, did not require any rejection of accepted principles, but merely a readjustment.