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° reflective goni- 

 [o meter. 

 P on P' 120° common " 

 F" on 11 120° " " 



Plane angle at a 44° " " 

 " " " h 136° " " 



From these, the plane an- 

 gles, and the inclination of theS 

 planes to each other, were 

 calculated. 



P on V" 142° 08' 20'' 



Pon/ 73° 10' 50'' 



Plane angles at A 38° 56-' 



a u a g 62° 29' 



" " I 78° 35' 



The axis is to the greater diagonal of the base, : : 3 : 2, and to 

 the shorter diagonal, : : 3 : 1 5 or more accm-ately, A A' : EE' : II' 

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

 perfectly accurate ; but rather as approximations. 



p" 



a 



Art. XVIII.—Ok the Transition Rocks of the Cataraqui ; by 

 Capt. R. H. BoNNYCASTLE, R. E. Canada. 



(Communicated for this Journal.) 



TO THE EDITOR. 



Sir — Conceiving that any circumstances tending to throw light 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. 



