On the Transition Rocks of the Cataraqul 



85 



\ 



inclination of one of these secondary, with one of the adjacent planes, 

 was determined by the reflective goniometer ; but no more of the 

 angles could be measured by this instrument, on account of the va- 

 por from the crystal affecting the eyes. 



P on n 120^ reflecdve goni 



[ometer 



P on P^ 120^ common 

 V on n 120^ 



u 



cc 



u 



Plane angle at a A4P " " 



From these, the plane an- 

 gles, and the inclination of theE('^ 

 planes to each"^ other, were 

 calculated. 



PonP 

 P onp' 



73° 10' 50" 



Plane angles at A 38° 56' 



" E 62° 29' 

 I 78° 35' 



Ci 



iC 



ic 



it 



a 



Jf 



and 



Q — Q — . — — , ^ 



the shorter diagonal, : : 3 : 1 ; or more accurately, A A' : EE^ : TF 

 :: 1 : .497 : .355. These measurements must not be considered as 



perfectly accurate; but rather as approximations. 



4_ 



Art. XVIIL — On the Transition Rocks of the Cataraqui; hy 



Capt. R. H. BoNNTCASTLE, R. E. Canada. 



(Commiinicated for this Jouinal.) 



TO THE ErlTOR, 



Sir — Conceiving that any circumstances tending to throw hght on 

 the ages of rocks, must prove interesting in the present state of geo- 

 logical science, and also apprehending that there are few which pre- 

 sent more singular appearances than those I am about to undertake 

 a feeble examination of, I have ventured to address you. 



c. 



