112 On a fulminating Comiination of Silver, 



their thighs, as they do (I believe invariably) the farina of" 

 plants. I have also frequently observed the combs of very 

 late swarms to be remarkably thin and u'hite, and brittle; 

 which are circumstances very favourable to the conclusion 

 that the wax is a vegetable substance, for it would probably 

 be less abundant during autumn than in summer ; and that 

 portion which had remained on the plants till late in the 

 season would hence become more colourless by exposure to 

 light, as well as more dry and brittle, than when at first ex- 

 uded ; but were it an animal substance, there does not ap- 

 pear any reason why it should be more dry and brittle, or 

 less abundant, in the autumn than in the spring and sum- 

 mer. The conclusions of Mr. Hunter are, however, always 

 drawn with so much caution, and he united so much skill 

 and science with the greatest degree of industry, that it is 

 not without much hesitation and diffidence that I venture 

 to put my opinion in opposition to his authority. 



T. A. Knight. 



Elton, 

 May 4, 1S07. 



XVIII. Notevpon a fuhnlnaihig Comhination of Silver, of a 

 white Colo2ir and a crystalline Appearance. By M. Des- 

 COSTILS *. 



X HERE is sold at Paris, as an object of amusement, a de- 

 tonating powder inclosed in slips of cards cut lengthways. 

 The powder is placed at one end of this carcase, and the 

 other end is made smaller in order to be more easily distin- 

 guished. If this last extremity is seized with one hand, and 

 the other end is held over the flame of a candle, a detona- 

 tion speedily takes place, with a sharp noise and a violet- 

 coloured flame ; the card is torn to pieces and scorched, and 

 the part which the composition touched is covered with a 

 slight metallic coating of a grayish white. 



Having been consulted upon the nature of this substance, 

 which is sent ready prepared to Paris, I v.-as convinced, after 



* From AnnnUs dc Chirrxie, torn. Ixii. p. 199. 



various 



