J34r 77EW MINERAt, 



tare below is reduced ; but as soon as it gets to 3<}^, the forc& 

 6f descent is weaker, and the quick application of cold shortly 

 reduces the marginal temperature to 32", or below, by which 

 the whole current is turned upwards; a slight diminution of 

 temperature at bottom isy notwithstanding, still perceived as 

 long as any water is found in the jar of 36", by its constant 

 superintendency downwards. 

 Conclusion. Thus I apprehend it is made appear that those uho have 



hitherto investigated the point of temperature at which water 

 is moit dense, from experiments of a similar nature to those 

 above, have mistaken it ; that the true point of greatest den- 

 sity is at36", and that the density at 32° and at 40°, or at any 

 other two equal intervals above and below 36°, is near}y the 

 same, progressively diminishing alike by the addition or ab- 

 straction of heat from the said point, 



I am your's, &c. 



J. DALTON. 



Mancliesler, May 12th, 1S06. 



VI. 



Analysis of a 

 aew niineral. 



Its historv. 



Analysis of a new Mineral found in Corimall. By J. Kidjd. 

 M. D. J^c. <^-c. 



To Mr. NICHOLSON. 

 SIR, 



^ Oxford, May gth, IS06, 



JJ. HAVE taken the liberty of sending you an account of the 

 analysis of a new mineral lately met with in Cornwall ; and, if 

 you think it of sufficient consequence, shall be obliged by your 

 giving it;a place in your Journal whenever it is convenient. 



The mineral in question was met with in one of the Gwennap 

 mines, and formed an incrustation round projecting particles of 

 a spongy pyrites intermixed with quart/5 ; this pyrites appeared 

 to contain a considerable proportion of cobalt, since it pro- 

 duced a deep blue colour when fused in a very small quantity 

 with glass of borax : the incrustation itself was supposed by 

 ihe miners to be a variety of wood-tin. Its appearance was 



altogeth(ir 



