MUSEUM OF COMrxVKATIVK ZOOLOGY. 



65 



rock may be so changed as to be taken by observers for a sedimentary 

 stratified one, even a good dolomitio limestone. The origin of the scr- 

 pentinoLis part by direct change in sUa of a peridotite (eruptive), as well 

 as by the filling of fissures iu the peridotite by serpcntinous material 

 derived from the surrounding rock, would seem in the main to be 

 consonant with the observations of Bonney, Bccke, Berwerth, Dathc, 

 Doelter, Drasche, lioehstetter, Koch, Lemberg, Sandberger, Strong, 

 Tschcnnak, Zirkcl, and others. Peridotite, wdiich we provisionally 

 classed with gabbro under basalt, in a preliminary publication ''On the 

 Classification of Rocks,"* it would seem from further and more extended 

 study, should be classed as a distinct species ; and some other rocks 

 may possibly belong with it. This species would represent a more basic 

 one than basalt, containing generally between thirty-five and forty-five 

 per cent of silica, or, more nearly, forty to forty-three per cent. The 

 reasons for this view it is intended to give fully in another publication, 



but they would be out of place here. 



The following analyses (incomplete) of this peridotite were made and 



published by Prof. Whitney : — 



Si02 



AbOa 



FcO 



MgO 



CuO 



Na20 

 H2O 



I. 



38.24 

 1.48 



31.50 



14.83 

 1.42 



BeteriiiiiKsd 

 with tbe iron. 



9.53 



II. 



3C.95 



III. 



37.25 



lY. 



16.50 



33.07 



6.75 

 14.14 



28. G7 



12.90 

 19.52 

 14.83 



.97 

 10.40 



100.00 



1.16 

 10.89 



98.86 



Analysis!, is taken from Foster and Whitney's Peport on the Geology 

 of Lake Superior, 11. 92. Analyses II., IIL, and IV., from the Ameri- 

 can Journal of Science, (2,) XXVIII. 18. 



Tliree miles and a half noiihwest of Ishpcming, or one mile and a half 

 west of Deer Lake, serpentine occnrs abundently on the land of Mr. 

 Julius Ropes, postmaster of Ishpeming.f This rock, altliough quite 

 hard, forms very l)eautiful specimens when polished (234, 235, 23C, 237, 



* Bull. Mus. Comp. Zoology, V. 279. 

 t First Annn;d Ecport of ilio Couuiussioncr 

 Midiigaii, pp. 204-200. 



VOL. VII. — NO. 1. 



of Mineral Statistics of the State of 



5 



