Atomic Weights
the proportions by weight in which the various elementary substances unite together. It is as the starting-point of the series and an necessary that one element be selected arbitrary sum affixed to it, so that thereby all the other elements can have their sums awarded to them, according to the bine with each other. The second law proportional amounts in which they commentioned under the atomic theory explains the manner in which this can be plains the manner in which this can be trary. In all systems of atomic weights in modern use, the atomic weight of hydrogen is taken as unity, and the atomic weight of the other elements are then fixed, so as to give on the whole the simfixed, so as to give on the whole the simtheir compounds. There are two systems of atomic weights at present in use: (1) The old system, which, after much discussion, was adopted about 1845; and (2) the new system, which is, in many respects, a revival of the system of Berrespects, a revival of the system of Ber- (2) the new system, which is, in many come into general use by scientific chemists about 1860. ATONEMENT ATROPOS