180 Dr. Uoget in Reply to Mr. Hume on his Test/or Arsenic. 



some years ago, for the detection of nmiute quantities of 

 arsenic. Lest any of your readers should be misled by the 

 assertions ot Mr. Hume, I beg leave to refer them to my 

 answer to his letter, which has appeared in the last number 

 of that Journal, ft will there be seen, that so far is the 

 charge of plagiarism from beino; well founded, that, in the 

 statement of which he complains, I have not only quoted 

 Mr. Hume's name, but have specifically pointed out his 

 claims to originality, and referred distinctlv, not only to the 

 document on which they rest, but also to a work, in which 

 a full account of all the modifications of his process, which 

 he afterwards published, is contained. To those who will 

 take the trouble of reading what Mr. Hume had written on 

 the subject previous to the appearance of my own paper, 

 it will be sufficiently evident that the mode proposed by 

 Dr. Marcet is essentially difftrent from any of those men- 

 tioned by Mr. Hume, who, in recommending the employ- 

 ment of nitrate of silver, has not even hinted at the possi- 

 bility of substituting ammonia for the fixed alkalies. In 

 inv answer to his letter I stated several reasons which led 

 me to prefer the former. This would now be a super- 

 fluous task, since Mr. Hume has himself become its pane- 

 gyrist; for i"n speaking of a test similar to Dr. Marcel's, 

 and whicli he calls the ammdniaco-nitratc of silver, he pro- 

 nounces that " it must now supersede all other tests for 

 arsenic, and become the standard to future operators." 



When a test similar to the one on which Mr. Hume has 

 bestowed this high eulogium first occurred to Dr. Marcet, 

 and when we ascertained together all the collateral circum- 

 stances mentioned in my paper res-pectins; the limits of its 

 power, and the agencies of other metallic bodies on the 

 same test, we had not the smallest knowledge or recollec- 

 tion of Mr. Hume'tf ever having turned his attention to the 

 subject of arsenic ; nor did any of the chemical friends, to 

 whom our experiments were shown, appear to have noticed 

 what he had written on the subject. It was only at the 

 moment of sending our remarks to the press, that Dr. 

 Marcet met with a quotation in Dr. Henry's Elements of 

 Chemistry, wnich led me to read the letters of Mr. Hume, 

 to whose claims I wis anxious to do, as I trust I have 

 done, every possible justice in the notice that I inserted ia 

 my paper. 



I am, sir, 



Your obedient servant, 



Bernard ?^treet, Russel Spare, p J^J_ RoGRT. 



Sei>t. 7, 1812. 



XXXIV. Cke^ 



