228 



PKOF. T. (x. BON.NEl' OX CRYSTALLINE SCHISTS AND THEIR 



Associated with the above rock, at its lower occurrence, is a 

 quartzose calc-schist, of which Dr. Grubenmann gives a description 

 and analysis * ; these show, as will presently be seen, that in 

 reality it differs little from some members of the Calc-mica schist 

 division. Indeed, I feel some doubt whether this '■' Disthen fuh- 

 ■render Schiefer ought not to be regarded rather as a member of 

 that division than as an equivalent of the staurolite and kyanite 

 rock near the eastern end of Lake Eitom. 



Tbe second zone of this Disthen fuhrender Schiefer (about 5 feet 

 thick) does not seem to differ materially in microscopic structure 

 from the first one ; and, like this, it is associated with quartzose and 

 calcareous schists. Tbe third zone {above the upper mass of the 

 rauchwacke), according to Dr. Grubenmann, very closely agrees (sehr 

 weitgehend uhereinstimmen) with the last named, although he has 

 not detected any disthene. Por myself, I may say that the rocks 

 appear macroscopieally identical. I could only distinguish speci- 

 mens by their labels, and agree with Dr. Grubenmann in not 

 attaching much weight to the absence of the disthene, a mineral 

 generally rather uncertain in its mode of occurrence. But, if iden- 

 tical, how is its presence outside the fold to be reconciled with his 

 theories ? 



Calc-mica Schist Division. 



The rocks included here vary from a fairly pure white or grey 

 marble to quartzose or micaceous calc-schists. If attention be paid 



Bidk analysh of the Schist contuining two Micas, Disthene, cf-c. 



I. II. 



SiO, 40-20 39-98 



TiO, 2-00 2-30 



Al.Pg 26-72 26-20 



Fe^Og 3-12 3-54 The ' ' Disthene:' 



^'^ l-?g J8? SiO. 36-85 



CaO 4-12 4-01 • ^i o fiS-l'> 



MgO 11-39 11-68 ^-^^3 t)ol^ 



l^^^ «-J2 «-^2 99.97 



Combustion-loss ... 2-22 2-18 ^P- S^'- =0^6^. 



100-54 100-18 

 Sp. gr. =3-0092. 



* " White aluminous Quart.:-sc7iist:' 



SiO, 25-99 



A1.,0, 8-95 



Fe;03 3-89 



CaO 29-70 



MgO 3-59 Sp. gr. =2-5792. 



K.,0 2-84 



Na„0 0-84 



CO; 23-86 



99-66 



This schist must accordiiigly_contain about 57 per ceut. (or, at any rate, more 

 than half) of carbonates (7'. r;.' /?.). 



