486 Mr. J. Bryce on Striated and Polished Rocks 



that both of these species of aloes also contain aloine, though 

 most probably contaminated with so much resin, or some 

 other substances, as prevents it from crystallizing. What 

 tends to confirm Mr. Smith in this opinion is the observation 

 he has made, that when the crude crystals of aloine are allowed 

 to remain in contact with the mother-liquor of the Barbadoes 

 aloes, they disappear and become uncrystallizable. I have 

 also observed a similar occurrence in the mother-liquors of 

 tolerably pure aloine. These become always darker and 

 darker ; so that if we continue to dissolve new quantities of 

 aloine in them, at length scarcely any of it crystallizes out, and 

 the whole becomes changed into a dark-coloured magma. 



In the year 1846, M. E. Robiquet published an account of 

 an examination he had made of Socotrine aloes. By treating 

 the concentrated aqueous solution of this species of aloes with 

 basic acetate of lead, he obtained a brownish yellow precipi- 

 tate, which was collected on a filter and washed with hot 

 water. On decomposing this lead compound with sulphu- 

 retted hydrogen and evaporating the solution to dryness, he 

 obtained an almost colourless varnish, consisting of a scaly 

 mass, which was not in the least degree crystalline. M. Ro- 

 biquet subjected this substance, which he called aloetine, to 

 analysis, and obtained the following result : — 



per cent. 

 8 C = 27-7 



14 H= 10-8 



10 O = 61*5 



100-0 



It is plain therefore that M. E. Robiquet's aloetine, if it 

 really is a definite organic principle, which I very much 

 question, is certainly a very different substance from the 

 aloine which has formed the subject of the present notice. 



Glasgow, Nov. 7, 1850. 



LXVIII. On Striated and Polished. Rods and "Roches Mou- 

 tonnees" in the Lake District of Westmoreland, By James 

 Bryce, jun., M.A., F.G.S* 



[With a Plate.] 



I. Introduction. 



THE lake district of Westmoreland and Cumberland has 

 received a very large share of attention from geologists. 

 Its rock-formations have been fully and accurately described, 

 * Communicated by the Author. 



