102 Description of the Steam Pyrometer. 
by weights. ‘The heat had been a moderately red heat ;—now, as 
cast iron has a specific heat of about .1212, this multiplied by 5668 
will give the equivalent weight of water =687, which heated to the 
same degree might produce the same effect. In the case just sta- 
ted, the quantity of water found to have been evaporated was 674. 
Hence 674 multiplied by the latent heat in steam, (=990° Fahr.) 
gives 667260° = the grains of water which would be heated one 
degree by condensing the steam now generated. But as the iron 
was equivalent to only 687 grains of water, it must have been heated 
as many degrees above 212°, as 687 is contained times in 6672609, 
which is 971.2 times; hence this number added to 212° will give 
the temperature of the iron, expressed in degrees of Fahrenheit’s 
scale, equal to 1183.2. 
2. Another experiment, conducted in the same manner, and with 
the same cylinder, but at a cherry red heat, gave 945 grains of steam. 
By applying to this case the principle of the formula, as before, we 
have, as above, 5668 X.1212=687, for the equivalent of the iron 
in weight of water; and 945 x990=935550 = the grains of water 
which would be heated one degree by the condensation of the steam 
produced. Then 935550~687=1362 = the number of degrees 
which the iron must have lost in producing this effect, while it came 
down from its initial temperature of redness to 212°. To this again 
we add 212°, and obtain 1574° for the actual temperature. 
3. A ball of cast iron, weighing 1665 grs., was heated to a bright 
red, and gave 230.2 grains of steam. Here 1665 X.1212=201.8 
= the equivalent weight of water, which, if heated to the same tem- 
perature, would have produced the same effect, viz. 230.2 x 990= 
227898. Now this divided by 201.8 gives 1128= the degrees 
above boiling point, at which the temperature was at first, or 1128-+- 
212 is equal to the actual temperature abore the zero of F’., viz.1340°. 
4. With the same ball, a second experiment gave 139 grains of 
steam. Hence 990X 139=137610, and this divided by 201.8=681.8, 
and to this add 212 and we have 893.8 for the temperature at first. 
5. The next experiment was with a cylinder of wrought iron, 
weighing 6110 grains, having a specific heat of .1100, and conse- 
quently being equivalent to 6110 X.11=672 grains of water. ‘The 
observed heat was a moderate red, and the loss in weight of water 
780 erains, whence the temperature must have been (780 X 990) 
-672 =1149+212=1361° Fah. 
6. The same cylinder was again employed, and raised to a bright 
red, so as to “scale” on exposure to the air. It then gave 989.6 
