602 ON DETECTING THE 
of the application of heat might with success be 
had recourse to in enabling us more positively to 
conclude of which of the two metals any crust 
or deposit we may have obtained is formed: and 
during the months of November and December 
last, I made repeated experiments, which, I 
think, proved the accuracy of the notion I enter- 
tained. Considering the readiness with which 
metallic arsenic volatilizes, and that it is said to 
be fusible at or below 400° of Fahr., while anti- 
mony requires about 800° for fusion, I thought it 
probable that there might be a wide thermometric 
range between the points at which the two metals 
were volatile or evaporable, and I commenced 
experimenting as follows. Having procured a 
number of slips of window glass, each about the 
1-10th or the 1-8th of an inch wide, and several 
inches long, I, by the aid of Marsh’s apparatus, 
caused metallic films, or crusts, of arsenic, to be 
deposited upon some of them, and of antimony 
upon others. I then provided a number of thin 
glass tubes, sealed at one end, and only about 
wide enough to admit the slips of window glass 
into them. Into one tube I put a slip of the 
window glass, coated thickly with arsenic, and into 
another a slip coated very thinly with antimony— 
in each case the slip being shorter than the tube, 
