OEIGIJSr OF CEYSTALLIISTE EOCKS. 7 



uncondensed, surrounded the globe with a dense envelope estimated to equal 250 atmos- 

 pheres. "The surface of the earth was at this time at a very high temperature, and if 

 silicates thou existed they must have been formed without the co-operation of liquid 

 water. Later, however, when it began to assume a liquid state, the water must have 

 reacted upon the pre-existing silicates upon which it reposed, and then have given rise to a 

 whole series of new products. By a veritable metamorphic action, the water of this primi- 

 tive ocean, penetrating the igneous masses, caused their ^irimitive characters to disappear, 

 and formed, as in our tubes, crystallized minerals from the matters which it was able to 

 dissolve. These matters, formed or suspended in the liquid, would then be precipitated, 

 and give rise to deposits presenting different characters as the temperature of the liquid 

 diminished." He then inquires: ""Were these different periods of chemical decomposition 

 and recomposition, in which aqueous action {la voie humide) intervenes under extreme con- 

 ditions which approach those of igneous action {la voie sèche), ÛiQ era of the formation of 

 granite and of the azoic and crystalline schists ? "We cannot affirm this in an absolute 

 manner, but we may presume it, especially when we consider that on this hypothesis there 

 must have been formed two principal products, the one massive and the other presenting 

 evidences of sedimentation, passing into each other gradually, as is the case with granite 

 and gneiss. In any case, it cannot be contested that if there was a time when the rocks 

 were exclusively under the dominion of fire, they passed under that of water at an epoch 

 much more remote than we have hitherto admitted. The influence, now established, of 

 water in the crystallization of silicates, no longer permits any doubt on this point. We 

 cannot perhaps now find anywhere upon the globe rocks of which it may be affirmed with 

 certainty that they have been formed by igneous action, without the intervention of 

 water." >» 



§ 15. To give some notion of the temperature of the first water precipitated on the 

 earth's cooling surface, Daubrée calcvilates that the waters of the present ocean, estimating 

 their mean depth at 3,500 metres, would, if spread uniformly over the earth's surface, have 

 a thickness of 2,563 metres, which, if converted into vapor, would correspond to a pressure 

 of 248 atmospheres, a weight which would be augmented by the presence of other vapors 

 and gases. " No liquid water coiild therefore rest upon the earth until its temperature 

 had fallen below that which would give to the vapor of water a tension of 250 atmos- 

 i:)heres," at least. When we consider that a tension of only fifty atmospheres of steam 

 corresponds, according to Arago and Dulong, to a temperature of 26589 centigrade, we can 

 form some conception of that corresponding to a tension five times as great ; which would, 

 on this hypothesis, have been the temperatui'e of the first waters precipitated on the cool- 

 ing planet, realizing many of the conditions attained by this ingenious experimenter when 

 he subjected mineral silicates to the action of water in tubes, at temperatures of from 

 400' to 500' centigrade. 



It is* unnecessary to point out that Daubrée here attempts to adapt Werner's neptunian 

 hypothesis to that of a once-fused and cooling globe, and to find, like Delabeche, in the 

 highly-heated primeval ocean, the chaotic liquid which, according to the master of Freiberg, 

 was the menstruum which at one time held in solution the elements of the primitive 

 rocks. The experiments of Daubvée in his tubes, above referred to, are of great impor- 



'"Paubrée, Études et Expériences Synthétiques, etc., pp. 121, 122. 



