It has been admitted by eminent geologists that the diamond proceeded from the slow decomposition of vegetable material, and even animal matter, as the requisite carbon could be obtained from either source. But they have also strenuously maintained that the gem was formed under the same conditions of heat as produced the metamorphism of argillaceous and arenaceous schists, these schists being supposed to have once been altered from shales impregnated with carbonaceous substances of organic origin. To this theory the revelations of the microscope offer decisive objections, since this instrument shows that there has been no action of heat in the formation of the stone, for the vegetable remains often detected in the interior of the mineral forbid the development of any considerable degree of caloric. Therefore, as there is no evidence of the influence or effect of heat upon these organic matters within the diamond, the theory must be abandoned. Geologists have been, perhaps, too tenacious in their views of the origin of many of the rocks that compose the earth’s crust, and especially in maintaining that many crystalline rocks are as old as the dawn of creation. We know that some of these minerals may be produced artificially at the present day, and that the forces that arranged all rocks of a high molecular organization are still in force. We sometimes speak of old crystalline rocks with the inference that their age is beyond comparison, and therefore undetermined. Yet the microscope is constantly lessening the force of these views by revealing prodigious numbers of minute and animal forms in fossil condition in various kinds of crystalline rocks. We also observe that various forms of silex have been deposited on the earth in recent periods of its history, and even since the appearance of animal life, for we find their remains transformed into agate. Thus it is evident that nature still possesses the power to deposit certain forms of mineral substances. Arago and Biot, reasoning from the energy of the refractive power of the diamond, were inclined to believe that it contained hydrogen. Sir Humphrey Davy suspected the presence of oxygen, but sought for it in vain after many careful experiments. Chaucourtois, however, deriving a theory from chemical results, came to the view that the stone is derived by the humid process from a hydrocarburet. Reasoning from the process of forming sulphur from hydro-sulphuretted emanations, he believed that in the humid oxidation of a carburetted hydrogen the hydrogen is oxidized, while part of the carbon becomes carbonic acid, and the rest remains as carbon and may crystallize into diamond.