386 Practical Distinctions in Minerals, 



There is a more serious objection still, in the fact that the 

 drawings are made, as stated in the prospectus, from her- 

 barium specimens (the instances to the contrary are few and 

 far between) ; and, though I am well aware it is a common 

 custom, especially upon the Continent, to make coloured 

 figures from such subjects, yet no one who reflects on the 

 different hues of living and dried specimens can, for a 

 moment, suppose that such are capable of representing the 

 natural tints ; and it is a practice which, in my opinion, can- 

 not be too strongly condemned. The Cryptogamia, gene- 

 rally speaking, however, offer a remarkable exception to this 

 rule ; so that few, if any, dried plants exhibit softer or more 

 agreeable colours for the exercise of the artist's pencil ; and I 

 would gladly publish the whole of that portion of the book 

 coloured, were I not satisfied, by sad experience, that, done 

 in the most economical way, the sale would not cover the 

 additional expenditure. 



No coloured botanical work ever was, or perhaps ever can 

 be, published at a cheaper rate than Mr. Curtis's Botanical 

 Magazine ; and it is only the much more extensive sale of it 

 (as compared with that of the Icones Plantarum) which can 

 justify the proprietor in offering it at so very low a price. 



I still flatter myself, from the favourable notice that has 

 been taken of the Icones Plantarum, both privately and in 

 several of the public scientific journals, that, notwithstanding 

 its deficiency (of which none can be more sensible than 

 myself), it will yet be found to answer the purpose intended, 

 — that of giving faithful representations of many new and 

 rare plants ; and that it will meet with such success as to en- 

 courage me to continue it beyond the second volume, which 

 is now nearly completed. — W, J. Hooker, Glasgow, June 

 9. 1837. 



Practical Distinctions in Minerals. — On March 31. 1836, 

 I discovered that the finest particles of mica and quartz in 

 stone may be readily distinguished without the aid of glasses; 

 and, conceiving that this simple method of knowing the dif- 

 ference in some of our most common minerals may be ser- 

 viceable to geologists ; I beg the insertion of it in your most 

 useful Magazine. 



With this view, therefore, without attempting any philo- 

 sophical explanation of the phenomenon, I merely relate the 

 circumstances of its practical application : first observing, 

 with pleasure, that the eye, which gives us the power of 

 knowing so much, and of knowing one thing from another so 

 distinctly, without our being able to explain how we make the 

 distinctions, is happily receiving from Sir David Brewster, 



