EXAMINATION OF SALT OF BITUMEN. 251 



of imitation affifted by theatrical action ; as Fitz James evidently 

 does, to a (battered audience, who cannot all, or even many 

 of them, be fuppofed to be duly placed for receiving one and 

 the fame echo : and upon a careful recollection of the pofitions, 

 I am much inclined to think none of them were fo placed. 

 The reflection of found by a fimple echo, — its more complicated Many pheno- 

 echo from a curved furface, or whifpering gallery, or fpeaking mena of foun4 

 trumpet, — its yet unexplained tranfmiffion along a fmooth wall deJufion ; but 

 or the furface of water, — its tranfmiffion through or along the how far ventri- 

 ground, fo well known to militarymen, and to which the firing of 

 Dr. Moyfe *, the fpeaking apparatus of Ezekiel Walker f, and 

 other fimilar effects, are referable. Thefe and other modes 

 of operation, unknown to or unthought of by me, may 

 furely be ufed in producing delufions and other ufeful or re- 

 markable effects, and may conftitute part of the art of ven- 

 triloquifm. I can only exprefs my opinion, that the art of the 

 profeffor I have fpoken of was exquifite mimicry, and nothing 

 more. 



VII. 



Examination ofthefo called Salt of Bitumen, the Bit-Nobin of the 

 Hindoos. By Frederick Accum, Practical Chemifi and 

 Teacher of Chemijlry. From the Author, 



IN the LV Number of Mr. Tilloch's Philofophical Maga- Account of 

 zine, p. 206, we find fome obfervations concerning a faline ? Jt dum ?' 5 ^ 

 compound lately imported from India, under the name of Salt Magazine, 

 of Bitumen or Bit-Nobin. From the experiments which the 

 author of that paper (Mr. Henderfon), made in order to be- 

 come acquainted with the nature of that fait, it appeared to fuppofed to be 

 him to be chiefly compofed of common fait and fulphurated^^^ 2 " 4 

 hidrogen gas. But as the experiments of this gentleman dohidrogen. 

 not appear to have been made with a view of affording an 

 analyfis of this faline fubftance, I was called upon by fome 

 medical practitioners of eminence to examine chemically the 

 nature of this curious compound. I (hall therefore confine 

 myfelf merely to this examination, which was conducted in the 

 following manner. 



* Philof. Journal. f Ibid. 



Upon 



