304 ORIGIN OF CRYSTALLINE ROCKS. [XIII. 



chlorite. The masses of Eozoon he found to be enclosed and 

 wrapped around by thin alternating layers of a green mag- 

 nesian silicate allied to picrosmine, and a brown non-magnesian 

 mineral, which proved to be a hydrous silicate of alumina, 

 ferrous oxide and alkalies, related to fahlunite, or more nearly 

 to jollyte in composition.* 



Still more recently, Dr. Dawson has detected a crystalline 

 silicated mineral insoluble in dilute acids, injecting the pores 

 of crinoidal stems and plates in a palaeozoic limestone from 

 New Brunswick, which is made up of organic remains. This 

 silicate, which, in decalcified specimens, exhibits in a beautiful 

 manner the intimate structure of these ancient crinoids, I have 

 found by analysis to be a hydrous silicate of alumina and 

 ferrous oxide, with magnesia and alkalies, closely related to 

 fa"hlunite and to jollyte. The microscopic examinations of Dr. 

 Dawson show that this silicate had injected the pores of the 

 crinoidal remains and some of the interstices of the associated 

 shell fragments before the introduction of the calcite which 

 cements the mass. I have since found a silicate almost identi- 

 cal with this occurring under similar conditions in a Silurian 

 limestone said to be from Llangedoc in Wales, t 



Giimbel, meanwhile, in the essay on the Laurentian rocks of 

 Bavaria, in 1866, already referred to, fully recognized the truth 

 of the views which I had put forward, both with regard to the 

 mineralogy of Eozoon and to the origin of the crystalline 

 schists. His results are still further detailed in his Geognost. 

 Beschreibung des ostbayerisches Grenzegebirges, 1868, p. 833. 

 Credner, moreover, as he tells us,J had already, from his min- 

 eralogical and lithological studies, been led to admit my views 

 as to the original formation of serpentine, pyroxene, and sim- 

 ilar silicates (which he cites from my paper of 1865, ali-ivt 

 referred to ), when he found that Gttmbel had arrived at 



* Jour. fur. Prakt. Chem., May, 1869 ; and American Journal of Science 

 (3), I. 378. 



t American Journal of Science (3), I. 379, and II. 57. 



t Hermann Credner; die Gleiderung der Eozoischen Fonnationsgnippe 

 Nord Amerikas. Halle, 1869. 



That in the Quar. Geol. Jour., XXI. 67. 



