182 REPORT— 1860. 



by magnesia, alumina, or glucina, gave crystallized quartz in the usual form 

 of the pyramidal hexagon, passing below into a silicate of the associated 

 bases. " The most remarkable part," as Daubree has remarked, " connected 

 with these reactions, in a chemical, arid especially a geological point of view, 

 is that the silicium and the silicates thus produced have an extreme tendency 

 to crystallize, and that the crystallization takes place at a temperature far 

 below their points of fusion." " The manner," he adds, " in which quartz and 

 the silicates are connected with the granite rocks has long been a difficulty 

 in all the hypotheses on the formation of the rocks called primitive. Now 

 we find, in our experiments, that quartz crystallizes at the same time with, 

 or even later than, the silicates at a temperature scarcely exceeding a cherry- 

 red heat, and consequently infinitely below its point of fusion." 



M. Daubree disclaims the supposition that those rocks themselves were 

 formed after the formula of his experiments. Nevertheless, considering 

 the probability that formations at higher temperatures, now obliterated, may 

 have preceded that of the granitic rocks, observing the uniform crystalliza- 

 tion of granite in the tenuity of its ramifications, as well as in mass, and 

 perceiving that Daubree by his process has reproduced almost all the granitic 

 minerals, and among them not only the felspar, but the crystalline quartz 

 of granite, — it must be admitted that such a theory is worth attention. 



Durocher has added to Daubree's researches two capital experiments, of 

 direct geological application, in obtaining the sulphides of the mineral veins 

 by the reaction of sulphuretted hydrogen on the chlorides of the metals in a 

 state of vapour, and in having effected the metamorphism of limestone into 

 dolomite in an atmosphere of the vapour of chloride of magnesium. 



A theory of sublimation, however, may admit of many modifications, 

 and may be combined with the principle of segregation illustrated in the 

 experiments of Ebelmen. Deville and Caron, having fused bone phosphate 

 at a l'ed heat in excess of chloride and fluoride of calcium, found that lime 

 apatite crystallized out in cooling, and was easily separated by washing from 

 the soluble salts. In like manner, with different bases and different chlorides, 

 they obtained the numerous varieties of apatite and wagnerite. And they 

 observed further, that all these minerals became volatile at a slightly elevated 

 temperature in the vapour of the chloride amidst which they were formed. 



Senarmont, pursuing another course, had applied a heat somewhat ex- 

 ceeding 662° Fahr. to an aqueous solution of hydrochlorate of alumina, con- 

 fined in a close tube, and thus decomposing it into its volatile and solid 

 ingredients, obtained corundum, distinctly crystallized and mixed with 

 diaspore, the same substance under a different form, and with different 

 chemical properties, thus repeating in a remarkable manner that process by 

 which the same minerals are found in nature similarly intermingled. He 

 also succeeded in eliminating crystals of quartz from hydrate of silica by 

 dissolving the hydrate in water charged with carbonic acid, and gradually 

 raising the temperature of the tube which contained it to a heat of from 

 400° to 500° Fahr., and by analogous methods he obtained carbonates and 

 sulphides identical with native minerals. In some of these experiments the 

 process was so varied as to show that the separation of the anhydrous cry- 

 stals was due to the gradual withdrawal of the dissolving gas. The hydrated 

 sesquioxide of iron, also heated in water of the temperature of 360° Fahr., 

 was dehydrated, becoming magnetic. In an experiment by Wohler, on the 

 contrary, apophyllite dissolved in water at the same temperature, returned 

 on cooling to its original form, retaining its water of crystallization. To this 

 class of discovery Daubree has likewise added some valuable facts, having 

 obtained regular crystals of quartz, by decomposing, with the vapour of 

 water alone, the interior of a glass tube subjected to a low red heat ; at the 



