54 



Of the Management of Fire 



and invisible that not the smallest appearance of cloudi- 

 ness was to be seen anywhere, not even about the ice, 

 which, as it went on to melt, appeared as clear and as 

 transparent as a piece of the finest rock crystal. 



This experiment, which I first made at Florence, in 

 the month of November, 1793, was repeated several 

 times in the presence of Lord Palmers ton, who was 

 then at Florence, and M. de Fontana.* 



In these experiments the air was not entirely expelled 

 from under the bottle ; on the contrary, a considerable 

 quantity of it remained mixed with the steam even after 

 the clouds had totally disappeared, as I found by a par- 

 ticular experiment made with a view to ascertain that 

 fact. But that circumstance does not render the result 

 of this experiment less curious ; on the contrary, I think 

 it tends to make it more surprising. It should seem 

 that neither the mass of steam, nor that of air, were at 

 all cooled by the body of ice which they surrounded ; for 



* The bottle made use of in this experiment, though it appeared very large 

 externally, contained but a very small quantity of water, owing to its bottom 

 being very much drawn inwards. As the hollow cavity under the bottom of the 

 bottle (which, as I just observed, was nearly in the form of a hemisphere, and 6 

 inches in diameter) served as a receiver for confining the steam which rose from 

 the boiling water in the plate, it may perhaps be imagined that a common glass 

 receiver in the form of a bell, such as are used in pneumatical experiments, 

 might answer as well as this bottle ; I thought so myself, but upon making the 

 experiment I found my mistake. A common receiver will answer perfectly well 

 for confining the steam, but the glass soon becomes so hot that the drops of 

 water which are formed upon its internal surface, in consequence of the con- 

 densation of the steam, instead of running down the sides of the receiver in clear 

 transparent streams, form blotches and streaks, which render the glass so opaque 

 that nothing can be seen distinctly through it ; and this of course completely 

 frustrates the main design of the experiment. But cold water in the bottle keep- 

 ing the glass cool, the condensation of the steam upon the sides of the hollow 

 cavity formed by the bottom of the bottle goes on more regularly, and the 

 streams of water which are continually running down the sides of the glass, 

 uniting together, form one transparent sheet of water, by which means every 

 thing that goes on under the bottle may be distinctly seen. 



