Platina and Mercury upon each other. log 
Royal Porcelain Manufactory of Berlin, in which Wedge wood’s 
pyrometer ceased to mark the degree of heat, they could not 
accomplish its fusion. Many of my friends in England have 
however seen the buttons which I obtained, and which were 
not few in number. The flux which I had used was borax. 
But no mention is made in any one of the operations of Mess. 
Rose and Gehlen of borax having been employed. 
In many of their attempts they obtained an irregular and 
porous mass, which of course was of a specific gravity much in- 
ferior to that of platina ; and it might be inferred from their paper 
that the diminution of specific gravity, which I had observed, 
was owing to the same cause. It is true, not only that I had 
very often obtained such a mass, but that I had frequently also 
observed no diminution whatsoever in the specific gravity of 
the button which resulted from my operations. But all those 
upon which I had founded the conclusions alluded to by Mess. 
Rose and Gehlen were performed in the following manner, 
and have been repeated since. A Hessian crucible was filled 
with lamp-black, and the contents pressed hard together. The 
lamp-black was then hollowed out to the shape of the crucible 
as far as one-third from the bottom, leaving that much filled 
with the compressed materials ; this lining, which adhered 
strongly to the sides of the crucible, was made extremely thin 
in order not to obstruct the passage of caloric. A cylindrical 
piece of wood, as a pencil, was then forced into the centre of 
the thick mass of lamp-black at the bottom, and the diameter 
of this rod was determined by the quantity of metal to be 
fused, or varied according to other circumstances at pleasure. 
In general the axis of the cylindrical hole was about three or 
four times the diameter of the basis. After withdrawing the 
