INTRODUCTION. 33 



such as a Delesseria alata. Beautiful as this was, it was 

 equalled, if not surpassed, by specimens given me by a 

 friend who gathered them at Tintock, a well-known hill iu 

 Lanarkshire. The stone was fine reddish felspar, and on 

 this delicate ground the dark crystallizations arose some 

 inches in height, much resembling a miniature grove of 

 elegant pine-trees. And these specimens, worthy of a place 

 in any cabinet, could be gathered in abundance, being 

 broken down for road-metal, soon to be trodden by the foot 

 of man and horse, or to be triturated by the crushing 

 wheels of aristocratic carriages or of heavy ignoble wains. 



It is rather curious that a few hours after I had written 

 the description of these beautiful crystallizations, I inci- 

 dentally got some insight into the way in which they are 

 formed in the great laboratory of Nature. The process, in 

 all likelihood, is known to many; but as it was a pleasant 

 little discovery to me, I shall mention it for the instruction 

 and amusement of some of my young friends who may be 

 as ignorant of the matter as I was myself. Having some 

 iodine in a hermetically sealed phial, I had occasionally 

 amused myself and others by heating the phial at the fire, 

 or at a candle or gas flame, and seeing it immediately filled 

 with most beautiful violet-coloured vapour. Wishing to 



