Description of the Steam Pyrometer. 101 
ean determine the specific heat, we may calculate the temperature 
as already indicated. I have, in this manner, proved the quantity of 
heat present in melted iron. Practical men may, possibly, from oc- 
casionally experiencing the tremendous effect of generating a quan- 
tity of steam from the moisture of their moulds, imagine that the ex- 
periment of pouring melted iron into a vessel of boiling water will 
be attended with danger. But I can assure them, from repeated 
trials, that it is perfectly safe. Plunge into a bucket of water, a 
common small iron kettle, supported on feet: pour into this, when 
completely immersed, any convenient quantity of melted iron; the 
ebullition from the surface of the melted mass will be at first very 
slow or scarcely perceptible, while from the outside of the kettle it 
will be very vigorous. The whole will subsequently exhibit the 
same effects as are perceived when a piece of cast iron is immersed 
at a bright red heat. 
The following experiment was made in August, 1831. Twelve 
ounces of melted iron were poured into about six pounds of water, 
at 212°: the result was eight ounces of steam produced. In 
order to calculate this case, and obtain the actual power present in 
the state of heat at the time of the immersion, we have to multiply 
the weight of steam by its latent heat, say 990°, which gives 7920° ; 
this divided by the weight of metal, (twelve ounces,) gives 660 for 
the number of ounces of water, which one ounce of the metal would 
have heated one degree, in cooling itself down to 212°. But as the 
temperature of the metal is the thing required, we must divide the 
above by the specific heat of cast iron, say 3.95 0 1212, which ~ 
gives 660—.1212=5445°. But it will be recollected, that a por- 
tion of this must be regarded as the latent heat of melted iron. 
In order to show what the latent heat of cast iron 7s, we may adopt 
the plan of taking from a mass of melting iron, a lump not actually 
liquefied, quench it, and observe the weight of steam produced. 
Again, pour from the same mass a portion of the liquefied metal, 
and ascertain how much more steam, for the same weight, is given 
by the latter than by the former. The same proceeding may be 
adopted for all other metals and their alloys. 
The following experiments and calculations will show the mode of 
applying the steam pyrometer. 
1. A cylinder of cast iron, weighing 5668 grs., was heated to red- 
ness. It was then placed within the receiver and instantly plunged 
into boiling water, previously accurately weighed; after the entire 
cessation of ebullition, it was withdrawn and the deficiency supplied 
