ACCOUNT OF A MINERAL SUBSTANCE. 129 



when tlie veifel was held near the hand but did not touch it. 



The fecond and third inftances of ventriloquifm afford ftrong 



proofs, that this delufive talent is nothing more than the art of 



i ubftituting an echo for the primary found ; for, befides the 



change perceivable in the direction of the voice, it was found 



to be blended with a variety of fecondary founds ; fuch as we 



know by experience are produced as often as a noife of any 



kind ifTues from a cavity. I have already made fome remarks Remarks ani 



on this fpecies of knowledge ; but it would be improper to obfervatlons « 



difmifs the fubject without noticing the accuracy, with which 



the ear recognizes the finer modifications of founds, and their 



caufes. I have frequently obferved; that a certain waterfall 



makes a flatter and duller noife when the ground is covered 



with 'fnow, than that which it affords at other feafons. The 



human voice alfo undergoes a fimilar change within doors, by 



ftriking a multiplicity of foft bodies, fuch as a number of piles 



of wool, or a crowded congregation in a church. 



The method of preventing the vibration of the vocal organs Difficulty not 

 from reaching the external teguments, is ftill wanting to com- folved » 

 plete this theory of ventriloquifm ; and I prefume it can only 

 be fupplied by an adept in the art. I mufl therefore difmifs 

 the fubject unnniflied, becaufe I have no pretention to that 

 character; 



XV. 



An Anah/fis of a Mineral Subjiance from North America, con* 

 taining a Metal hitherto unknown . IfyCkARLEsHAtCHETT, 

 Efq.*. 



I 



N the courfe of the laft fumrrier, when f was examining Specimen of mi- 

 and arranging fome minerals in the Britifh Mufeum, I ob- neral ob f e rved in 



rved a fmdll fpecimen of a dark-coloured heavy fubftance, f eU m. 



rhich attracted my attention, on account of fome refemblance 

 which it had with the Siberian chromate of iron, on which at 

 that time I was making experiments. 



Upon referring to Sir Hans Sloane's catalogue, I found that Hiftorical par* * 

 this fpecimen was only defcribed as " a very heavy black ftone, cu,a "» 



Philof. Tranf. 1802. 

 Vei II,— Junk, 1802, K « with 



