ORIGIN OF CEYSTALLINB ROCKS. 19 



sequent hydration aud metasomatosis, has been changed to banxite, diaspore, spinel, opal, 

 and a gTeat number of aluminiferotis silicates, including various micas, probably some 

 feldspars, aud also magnesian silicates of the chloritic group. The final result has been, 

 " in many instances, a pretty thorough alteration of the original corundum into micaceous 

 and chloritic schists or beds, or, as Prof Dana would express it, ' a pseudomorphism on a 

 broad scale.' " " 



§ 38. Julien, who has more recently studied these rocks, adopts with regard to the 

 chrysolite-beds the view suggested by Clarence King, in ISYS, that they were derived 

 from the disintegration of chrysolitic eruptive rocks, and were originally chrysolite sand- 

 stones. Chrysolite, according to him, and not corundum, has been the point of departure 

 for the various changes which have given rise to the crystalline schists in question. Thus, 

 while some of the chrysolite beds remain unchanged, others have been converted into 

 strata of cellular chalcedonic quartz, of serpentine, of steatite, of talcose actinolite-schist, 

 of tremolite schist, and of a diorite or gabbro made of albite and smaragdite aud including 

 grains of red corundum, sometimes with margarite. Within these rocks are veins and 

 fissures of various sizes and shapes, in which are found crystallized corundum, with ensta- 

 tite, actinolite, talc and ripidolite, among other species. Julien, who assigns a similar 

 origin to the like crystalline schists found elsewhere throughout the Atlantic belt, con- 

 cludes that all of these various rocks have been derived from chrysolite. As regards the 

 hypothesis of Grenth, he writes : " The view which has been suggested, founded on certain 

 phenomena observed in the corundum-veins, that these secondary rocks, and many schists, 

 have been derived from the alteration of corundum, finds not the least confirmation from 

 my studies, and is indeed strongly contradicted by facts observed in the field. The corun- 

 dum itself is, in all cases, both in the veins and in the particles found in the gabbro, a 

 secondary or alteration-product. All the phenomena of alteration, both in the veins and 

 rock-masses absolutely require, aud can be simply explained by the introduction of a solu- 

 tion of soda aud alumina into the fissures and interstices, during the period of alteration and 

 metamorphism." " This solution, he imagines to have come from some subterranean sovirce 



"Genth, Proc. Amer. Philos. Soc, Sept. 1873 and July 1874; also Amer. Jour. Soi. (3), vi., 401 and viii., 221- 

 223. Mr. Dana, in a notice of Dr. Genth's conclusions, in the last citation, denounces me severely for having, on a 

 former occasion, cited from him the words above quoted by Genth, forgetting that it is Genth, whom he 

 praises, and not myself, who is thus attributing them to him, and that Grenth's conclusions, if admitted, form a 

 striking exemplification of that doctrine, which Dana there repudiates. In the same note, after stating that I have 

 declared that " the advocates of the doctrine of transmutation " have taught that " the greater part of all the 

 so-called metamorphic or crystalline rocks are the result of an epigenic process," and that " the advocates of this 

 doctrine maintain that a mass of granite or diorite may be converteii into serpentine or limestone, and that a lime- 

 stone may bo changed into granite or gneiss, which may in its turn become serpentine," Dana calls this an extra- 

 vagant doctrine, and says : — " I demonstrated that all writers on pseudomorphism, with but one or two exceptions, 

 would repudiate it as strongly as myself." He farther says the statements here quoted " have been shown by me 

 to be untrue ;" and, with regard to the transmutation of granite or gneiss into limestone, declares, in repeat- 

 ing his charges before the Boston Society of Natural History, that " he never knew any one ignorant enough or 

 audacious enough to have suggested it." (Proc. Boston Soc. Nat. Hist., xvii. p. 170.) 



Those who read these pages, and will take the trouble to consult the authorities here cited, or those given in 

 more detail in my Chemical and Geological Essays, pp. 324-326, may satisfy themselves that I have not borne false 

 witness in this matter, but that every one of the changes cited has been formally maintained by some one or more 

 of the transmutationisfs. It is suroly not more difficult to transform granite into limestone, than limestone to 

 granite, as imagined by Volger, or corundum to opal with Genth, or chrysolite to corundum with Julien, 



" Proc. Boston Soc. Nat. Hist. (1883) vol. xxiii, p. 147. 



