in 1815, with no author's signature, in Thomson's 'Annals of Philosophy.' Prout had noticed that the 'atomic weights of many of the lighter elements seemed to be exact multiples of that of hydrogen; hence he made the suggestion that all the different atoms may be merely aggregations of the simple hydrogen atom, and that this hydrogen atom is really the primitive element from which all other substances are made.
This was the first attempt to determine a relation between the apparently different kinds of matter, and it was more than eighty years before the advocates of the theory were finally forced to abandon it. There have been few laws in chemistry, and certainly no false hypotheses, which have given rise to so much investigation as that which has been occasioned by Prout's hypothesis. That it could have 60 long retained adherents among chemists, many of them men of great prominence, is due to the fact that it seems on its face to be true. When it was first published, a very considerable number of the atomic weights were approximately multiples of the weight of the hydrogen atom, far more than could be accounted for by chance. It seemed reasonable to believe that, with the meager facilities for accurate work at that day, the atoms of the few other elements would prove, when they should be accurately determined, to be also exact multiples of the hydrogen atom. This view was held by many chemists until a Belgian chemist, Jean Servais Stas, undertook to determine the atomic weight of a few of the elements with an accuracy far greater than had been known up to that time. Prout's hypothesis had been sustained by rounding off the decimals to whole numbers; Stas, before he began this work an earnest believer in the hypothesis, endeavored to determine at least one place of decimals so accurately that it could not hereafter be neglected, and his work is one of the classics of chemistry. He proved clearly that the atoms of several elements, at least, could not be multiples of that of hydrogen. Some of the supporters of the hypothesis then assumed that it was not the hydrogen atom, but a half of it, or some other fraction, which is the original matter, from which all other atoms are derived. The hypothesis may be said to have finally ended its long career when Professor Morley, of Adelbert College, showed that there is no simple ratio between the atomic weights of oxygen and hydrogen; that, instead of being 16:1, it is 15.879:1. For accuracy Professor Morley's work may be justly compared with that of Stas, but in conception of experiment and in difficulty of execution it far surpasses that of the Belgian chemist.
But while it may be considered as absolutely proved that a large share of the atoms have weights which are not exact multiples of that of hydrogen, yet it remains true that many of those which have been determined with the greatest degree of certainty do approach with
