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INTRODUCTORY                              5
yielded or is now yielding up its secrets with more or less freedom to the scientist. By his method of synthesis (which is the scientific name for putting substances together in order to form new compounds out of their union) or of analysis (the decomposing of bodies so as to divide or separate them into substances of less complexity), particularly the latter, he slowly and surely breaks down the substances undergoing examination into their various constituents, reducing these still further till no more re­duction is possible, and he arrives at their elements. From their behaviour during the many and varied processes through which they have passed he finds out, with unen-ing accuracy, the exact proportions of their composition, and, in many cases, the cause of their origin.
It may be thought that, knowing all this, it is strange that man does not himself manufacture these rare gems, such as the diamond, but so far he has only succeeded in milking a few of microscopic size, altogether useless except as scientific curiosities. The manner in which these minute gems and spurious stones are manufactured, and the methods by which they may readily be distinguished from real, will be dealt with in due course.
The natural stones represent the slow chemical action of water, decay, and association with, or near, other chemical substances or elements, combined with the action of millions of years of time, and the unceasing enormous pressure during that time of thousands, per­haps millions, of tons of earth, rock, and the like, sub­jected, for a certain portion at least of that period, to extremes of heat or cold, all of which determine the