372 Reviews — Capt. C. E. Button — 



a liquid state. Yet this limit is presumably receding with the 

 secular cooling of the earth into lower depths. Whether the inverse 

 j)rocess — the elimination of water from the lower depths to which 

 they may have penetrated — is possible, thereby constituting a 

 diminution of mass, is a question which will be alluded to further on.^ 



Having thus alluded to causes leading to change of mass, the 

 author proceeds to discuss those which may affect the density, and it 

 is here that the novelty of his suggestions appears. 



Change of density due to secular cooling alone has been shown to 

 be unimportant. Yet there is another possible cause which seems 

 to have been quite overlooked, and if it should prove to be a vera 

 causa, its importance will be immense. It has lately been estab- 

 lished that water, under requisite conditions of heat and temperature, 

 has a powerful chemical reaction upon the materials of which the 

 ordinary rocks are comj)osed. M. Daubree enclosed various minerals 

 in thick- walled tubes of iron containing water, and sealed hermeti- 

 callj^ by welding. The tubes were then exposed to temperatures of 

 600^ F. and more, for a number of days, and after cooling were 

 opened and examined. It was found that the water had acted very 

 energetically upon the enclosed substances, breaking up their 

 original combinations, and that new crystalline substances had been 

 formed. Thus common glass and clay, which contain the chief 

 elements which make up the rocks of the earth, were converted into 

 felspar, mica, quartz, and hornblende, which are the chief minerals 

 of the crystalline rocks. These experiments were quickly followed 

 by others of a similar character, all leading to the same conclusion — 

 that water reacts energetically, even at moderately elevated tem- 

 peratures, upon minerals which are not sensibly attacked by it at 

 lower ones ; and that siliceous compounds in a vitreous condition, 

 like glass, obsidian, and many lavas, as well as many materials 

 which are found in sedimentary rocks, are broken up and recon- 

 structed into new crystalline forms. Metamorphism then does not 

 require a temperature sufficient to produce dry fusion. The required 

 changes may take place at a heat below redness, though it can 

 hardly be doubted that the reaction of water, and its solvent j)Ower, 

 increase with the heat, so long as the pressure is sufficient to keep 

 it in its liquid form. In the course of these experiments it was 

 observed that the minerals in their transformation exhibited changes 

 of density, which were sometimes surprising. It is considered 

 probable that minerals in this state of " hydrothermal solution " are 

 swollen and bulky, taking a form similar to that presented by silica 

 in the gelatinous condition, and alumina in the hydrated state. 

 These hydrated minerals are of a considerably lower sjoecific 

 gravity than their corresj^onding crystals, and in general all earthy 

 materials are less dense in the amorphous (uncrystalline) than in the 

 crystalline state. The admixture of water would obviously render 

 the former still less dense, and such is known to be the case. 



^ "We do not however perceive that this question, to which we are disposed to 

 attribute great importance, believing with the late Mr. Scrope that the water 

 eliminated by volcanos is an original constituent of the nucleus, has been adequately, 

 if at all, discussed by Captain Button. 



