Dr. Guy, on Microscopic Sublimates. 13 



and beauty of form, no less than for the magical quickness 

 with which they spring up and spread. Their colour, again, 

 is peculiar, and may be fitly compared to that of smoked 

 quartz; and they often rest upon a uniform brown layer, 

 which cracks as it dries, and throws off the crystals, which 

 adhere lightly to its surface. The finest crystals are often 

 yielded by the smoked variety of sublimate. They are some- 

 times detached masses tilted upwards, nearly circular, like 

 grindstones ; but they often assume the form of such insects as 

 the dragon-fly, the wings being beautifully marked with 

 radiating lines. In the dry spot they become, as it were, en- 

 tangled in the brown cracked layer of which I have just 

 spoken (fig. 25). The reactions with ammonia (fig. 24) and 

 spirits of wine (fig, 23) show some curious crystalline forms ; 

 andthe large drops of the smoked sublimate are sometimes filled 

 with dark tracings. These drops, too, show these dark tracings 

 instantaneously, on the addition of carbazotic acid (fig. 21). 



Of morphine sublimates it may be stated, that they con- 

 trast with those of strychnine by their greater solubility no 

 less than by the size, brilliancy, and strange forms of the 

 crystals which result from their reactions. 



Of the other alkaloids I have little to say at present. I 

 content myself with showing photographs of two of their 

 number — meconine, with its tufts; and the new alkaloid, 

 cryptopia, with its beautiful stellate patterns (figs. 7 and 8) . 

 I also show one photograph of the sublimate of an animal 

 product — Mppuric acid (fig. 9) . 



I now bring this paper to a close, and trust that the 

 Society will accept it as a brief, though not a careless or 

 superficial introduction to a large and very important subject, 

 in the treatment of which I may claim to have had very 

 considerable experience of the peculiar niethod of sublima- 

 tion which it has been my desire to explain and recommend. 



*^* It may be well to explain that the paper, when read to the 

 Society, was illustrated by a series of admirable microphotographs by my 

 friends, Dr. Julius Pollock and Dr. Maddox, from which photographs, aided 

 by the objects themselves, the drawings of Mr. Tuffen West were made. 

 These illustrations, equally faithful and artistic, may be found in one or two 

 instances not to correspond ])recisely to my verbal description in the text. 

 Where this is the case, the verbal description must be preferred, as it is 

 based on the examination of many specimens, and fairly portrays their gene- 

 ral features. For the specimens of the alkaloids which have yielded the 

 sublimates, I am indebted to the Messrs. Morsou, with the exception of the 

 new alkaloid, Cryptopia, kindly given to me by my friend Dr. Cooke, of 

 King's College. 



