various parts of Scotland. 431 



any change of their direction or appearance, marking clearly a 

 common condition in the schist and the quartz, at the period of 

 their formation. It is also worthy of remark, as I have observed, 

 in another place, in speaking of the rutile of Killin, that although 

 the crystals of disthene in general penetrate and impress the quartz, 

 they are sometimes bent and waved as if they had accommodated 

 themselves to its irregularities. Ignorant as we still are of the 

 mode in which various minerals are crystallized together, it is not 

 Uxi worthy of our attention to collect all the facts which may tend 

 ultimately to throw light on this obscure process. 



The clay slate which I have mentioned above, constitutes a large 

 portion of the mountains which here form the termination of one 

 of the Grampian branches in this direction ; it is succeeded by a 

 hard quartzy sandstone, similar to the rock of Assynt, before 

 described, and by an exceedingly hard quartz breccia, in which 

 the paste is led, and the fragments white, and which is noted for 

 containing agates and jaspers. Immediately after this follows the 

 red sandstone, which constitutes a great part of the flat tract of 

 Moray, and bounds the course of the Spey in this place. It is 

 accompanied by the singular rock above alluded to, which I am 

 about to describe. This rock consists of a talcy clay slate, so 

 penetrated with hornblende as to render its character for an instant 

 doubtful. On an accurate examination, it will be seen that the 

 body of the rock is a clay slate, and that it is interspersed throughout 

 with lamellar and thin crystals of hornblende. These lamellse 

 are generally disposed at right angles to the lamellse of the schist, 

 and are sometimes short and straight, and variously placed, inter- 

 fering with each other in every direction. More commonly they 

 diverge from a sort of central axis. In curved planes, so that their 

 section according to the lamellae of the schist, exhibits an appearance 



