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instrument. Two glass bulbs — one holding an interior tube 
for the reception of the substances, and the other a little 
smaller in diameter in order that its cubic contents may be 
about the same — are fitted with an index tube of small bore, 
as shown in the figure, which is graduated between the two 
small cavities on the upper portion of the tube — the cavi- 
ties being there to prevent the index being accidentally 
drawn into either of the bulbs. The two bulbs are placed 
in a box (indicated by dotted lines) surrounded by non-con- 
ducting material, and the instrument is ready at any time 
for use. A thermometer is placed between the bulbs in 
order that the temperature may be noted at which the ex- 
periment was tried. In the instrument No. I. the indica- 
tions are nearly proportional to the specific heat of the 
substance, but in the second or differential calorimeter a 
curve should be drawn of the values for known metals just 
as is done for the spectroscopic scale, and the specific heats 
of the bodies reduced by reference to the curve. To 
show the accuracy of the instruments I give here some 
specific heats taken at random from many I have done. 
First, by No. 1 Calorimeter : — 
Substance. 
Found 
Correct Numbers. 
Arsenic 
•0820 
•0814 
Tin 
■0575 
•05623 
Platinum 
•0339 
•0335 
Bismuth 
•0315 
•03084 
I should say that I took as my standards to draw the 
reference curve the following metals : — 
Lead 
•03065 
Silver 
•05701 
Zinc 
*09555 
Iron 
•11380 
Magnesium 
•2499 
The Differential Calorimeter 
gave : — 
Substance. 
Found 
Correct Numbers. 
Arsenic 
•0818 
•0814 
Tin 
•0565 
•05623 
Platinum 
•0338 
•0335 
Bismuth 
•0309 
•03084 
