FOR MEASURING THE EXPANSION OF SOLIDS. 
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exhibit but little signs of liquidity till subjected to a heat much above its 
true point of fusion. When once in a liquid state, both would rapidly rise to 
the temperature of the medium to which they were exposed. When metals are 
melted for the purposes of the arts, they of course require to be heated very 
far beyond their fusing points, that they may flow into the minutest fissures of 
the moulds in which they are cast, notwithstanding the cooling influences to 
which they are suddenly exposed. In some of the finer castings of brass, the 
perfection of the work depends upon the intensity to which the metal is heated, 
which in some cases is urged even beyond the melting point of iron. With a 
fire whose power in all cases must so greatly exceed the temperature required, 
it is necessaiy to bestow great care in supplying the metal gradually, as we 
have before described ; as it is inconceivable with what rapidity it rises after 
the solid pieces are completely dissolved. Evidence of the same fact may be 
derived from the experiments of MM. Clement and Desormes, which I have 
before quoted. They calculated the heat of melted iron at 3988°, and of iron 
just on the point of melting at 3164°,— a difference of 800°. And it is clear from 
the circumstances of the experiment, that the former must have considerably 
exceeded the true melting point, or it never could have been transported in a 
liquid state from the crucible to the apparatus in which the water was heated 
or the ice melted. It is probable that the process which they employed, of the 
calorimeter, was not susceptible of great accuracy ; but the discrepancy of the 
results from those which I obtained from the metal in analogous circumstances 
is not great. 
Iron just melting .... 3164° by the former 
2889 by Pyrometer 
275° difference. 
Iron melted at a high heat . 3988 by the former 
34/9 by Pyrometer 
509° difference. 
A similar excess also appears in their determination of the heat of melted 
copper, and obviously admits of the same explanation. 
After performing these experiments upon the melting points of the metals, I 
was desirous of ascertaining the effects of the most intense heat which it was 
possible to produce in a furnace ; and to measure the utmost limits of expansion 
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