406 SEVENTH REPORT—1837. 
porting 392lbs.; the deflection is even greater in the latter, 
arising in all probability from a greater degree of ductility in 
* the bars. 
I hope shortly to induce my friend Mr. Hodgkinson, Profess- 
or Barlow, or some other able mathematician, to investigate this 
subject, and by close analysis to demonstrate those truths, so 
essential to the interests of all engaged in the use of the metals, 
but more particularly in reference to the security oi the public 
at large. 
Effects of Temperature. 
When the multiplicity of objects to which cast iron is ap- 
plied, and the innumerable situations in which it is placed, is 
considered, I may venture to state, that in every work of which 
cast iron forms the whole or a part of the structure, it is more 
or less liable to change. The rapidity with which it imbibes, 
and the facility with which it parts with caloric, is in itself a 
sufficient consideration for the labour I have bestowed upon 
these inquiries. 
The present investigation would have been less satisfactory 
had the experiments on the effects of temperature been omitted ; 
and I trust, the annexed Tables, which exhibit hot and cold blast 
iron under various gradations of heat, will not be without their 
uses in the future application of this material. 
Rondelet, in his ‘* Traite de Bdtir,’”’ has given and collected 
results from experiments, made by himself and others, on the 
expansion of bodies under the effects of heat; but I am not 
aware of any that have been made to ascertain the transverse 
strength of metallic substances under the various changes of 
temperature. Itis well known that the effects of heat upon iron 
have not escaped the notice of philosophers; but I believe no 
writers on this subject have conducted their experiments in any 
way analogous to those now under consideration. 
The celerity with which heat passes through the metals, and 
the frequent recurrence of iron being the medium of communi- 
cation between fluids and this powerful agent, it is not surpri- 
sing that the changes of temperature thus induced should cause 
such visible indications of deterioration in the material. Gas 
retorts, and all those vessels exposed to the alternate changes 
of the heating and cooling process, are considerably injured by 
the expansion and contraction of the parts; and no doubt the 
destruction of the metals is much accelerated when they are 
worked up to a high and excessive temperature. Probably 
steam-boilers are not so much injured as those above-men- 
tioned, as the temperature is kept moderately low by the water 
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