Volcanos. 141 



sandstones, &c. he attributes solely to a concretionary action, 

 accompanied by a more or less imperfect crystallization of the 

 very finest particles which act as a cement to the coarser. 

 The -more complete the process of crystallization, the more sol- 

 id and campact the rock ; and therefore the larger the propor- 

 tion of precipitated matter, (which as being much finer than 

 any sediment, is more favorable to crystallization,) the more 

 crystalline and the harder will be the strata. It is well known 

 thyt, amongst the stratified rocks, the older are generally the 

 most crystalline, and hence we should expect the quantity of 

 matter precipitated by the waters of the ocean to have been 

 greater in former times than now. The author attributes this 

 to t e higher temperature of the ocean in those ages, and the 

 greater quantity of mineral matter earned into it in a state of 

 solution by the vapors evolved from the interior of the globe. 

 Even the more completely crystalline rocks, such as statua- 

 ry limestone, quartz rock, and rock salt, appear to the author, 

 in the light of precipitations from the primitive ocean, where at 

 this time the sedimentary matter predominated, mica, talc, and 

 chlorite slates were deposited. With regard to gneiss, the low- 

 est of the stratified rocks, the author considers it to share in 

 a very slight degree in the character of a sedimental rock, to have 

 been in short a granite, which, after a great degree of intu- 

 mescense, was reconsolidated by the pressure it sustained be- 

 tween the expansive force of the granite beneath, and the 

 weight of the solid strata which had settled above it, as well as 

 of the ocean and atmosphere. 



" The author then generalizes these views as to the origin of 

 the different rock formations, in a " Sketch of a Theory of the 

 Globe," of which the following is a brief abstract. 



fct The mass of the globe, or at least its external zone, to a great 

 depth, is supposed to have been originally granitic, and that, on 

 reaching its actual orbit, perhaps before, a great proportion of 

 the pressure was removed which had previously preserved it in 

 a state of crystallization, notwithstanding its intense temperature, 

 (perhaps as an integrant part of the sun, from which the author 

 is inclined to think it a projected fragment,) according to the 

 notion of Buffon and Laplace.* Violent superficial expansion 

 was the result of this diminished compression ; the dilitation de- 

 creasing towards the interior, from the surface, which would be 

 completely volatilized to that point where the disaggregation of 

 the granite was wholly checked by the pressure of the zone of 



* The author, in a note, compares the globe at this time to an aero- 

 lite, in which the superficial crust of vitrified matter bears some analo- 

 gy to that which then perhaps formed on the surface of our planet. 



