340 ANNUAL OF SCIENTIFIC DISCOVERY. 



and wrinkles of lava streams ; and though no telescope has yet seen them, 

 nor perhaps can expect to do so, unless mounted on such a peak as Tene- 

 riffe, high above the clouds and the tremors of the atmosphere, yet the secu- 

 rity which the discovery of such a fact would give to investigations into the 

 moon's physical history, might render the attempt well worthy of attention. 



GEOLOGY OF CRYSTALS. 



An interesting paper on this subject was recently read before the Geolog- 

 ical Society of London, by H. C. Sorby, F. R. S., in which his experience in 

 the microscopical examination of crystals was given. In some of these, dry 

 cells are found; in others there are water cavities. Crystals having cavities 

 with water, he concludes, were formed from aqueous solutions ; crystals con- 

 taining dry cavities were formed from matter in a state of igneous fusion ; 

 crystals containing both water and dry cavities were formed under great 

 pressure, by the combined influence of highly heated water and melted rock. 

 The amount of water in some of these cavities may be employed to deduce 

 the temperature at which the crystals were formed; those containing few 

 cavities were formed more slowly than those containing many. 



Applying these general principles to the study of natural crystalline rocks, 

 minerals, etc., it appears that the fluid cavities in rock-salt, in some calcare- 

 ous spar, in limestone, and in some gypsum, indicate that these minerals 

 were formed by deposition from solution in water, at a moderate temperature, 

 and the same conclusions apply to other minerals in veins in various rocks. 

 The constituent minerals of mica-schist and the associated rocks contain 

 many fluid cavities, which indicate that they were metamorphosed by the 

 action of heated water, and not by mere dry heat and partial fusion, as tho 

 plutonist geologists have taught. 



The structiire of minerals in erupted lava proves that they were deposited 

 from a mass in a state of igneous fusion, like the crystals in the slags of fur- 

 naces; but in some blocks projected from volcanoes there are water as well 

 as dry cavities, which indicate that they were formed under pressure at a dull 

 red heat, when both water and liquid rock were present. Quartz in veins 

 has a structure proving that it has been rapidly deposited from a solution in 

 water, and sometimes at a high heat (about 329 Fah.), and when the tem- 

 perature was greater, mica, tinstone, and even felspar were deposited. Solid 

 granite, far from contact with stratified rocks, sometimes contains fluid cav- 

 ities; this is especially the case with coarse-grained quartzoze granites, in 

 which the water constitutes two per cent, of the volume of the quartz, and the 

 cavities are so numerous and minute as to number thousands in a cubic inch ; 

 felspar and quartz in this granite contain dry cavities, thus showing that 

 these minerals were formed with water under fusion of high temperatures. 

 The conclusion arrived at from this is, that granite is not a simple igneous 

 rock, formed as geologists have generally taught, when the earth was a mass 

 of fire, and when no water could be found resting upon its surface. 



ON SOME PECULIARITIES IN THE ARRANGEMENT OF MINERALS IN 



IGNEOUS ROCKS. 



In a paper on the above subject, read before the British Association, 1858, 

 by Mr. H. C. Sorby, he stated, " that very often, in igneous rocks, infusible 

 minerals had been formed upon such as were far more fusible ; which was a 

 very unintelligible peculiarity, if they supposed that the temperature at 



