514? 
Dr. Schafhaeuti on the Different Species of 
are admitted, the value of E different from zero shows that 
the absolute heat is not constant ; but the preceding theory 
does not appear to me to furnish the means of determining the 
value of Z), and hence of deciding with certainty whether the 
latent heat is constant, and whether in augmentations of heat 
the sensible heat only varies. I think there can be little 
doubt that the conditions assumed by Laplace actually ob- 
tain, and that the hypothesis attributed to Watt* must be aban- 
doned. The experiments recorded by Mr. Parkes in the 
3rd volume of the Transactions of the Society of Civil Engi- 
neers, p. 71, which show that the quantity of fuel required to 
evaporate a given weight of water is nearly the same what- 
ever be the pressure of the steam, do not seem to me to au- 
thorize a different conclusion. For this is precisely what 
would take place if the latent heat be constant, and if the 
quantity of fuel required to generate the latent greatly exceed 
that required to generate the concomitant sensible heat. 
The quantity y has never before been determined for 
steamf or for the vapour of any liquid, properly so called, 
as far as I am aware. It may excite surprise that the value 
of y should come out less than unity. Both Poisson and 
Dulong assert that it is evident that y must surpass unity, 
but the reason which they assign appears to me inconclusive. 
[To be continued.] 
LXXIX. On the Combinations of Carbon mth Silicon and 
Iron, and other Metals, forming the different Species of Cast 
Iron, Steel, and Malleable Iron, By Dr. C. Schafhaeutl, 
of Munich, 
[Continued from p. 434.] 
^I^HE brown residuums of all white irons, when boiled with 
hydrochloric acid before ignition, parted with their iron 
with extreme difficulty. In one trial after boiling the mixture 
in a bottle whose neck vvas shut up with a capillary tube ; first 
no apparent change took place, and only hydrochloric acid 
escaped; after boiling an hour the contents of the bottle began 
to become thickish, a disagreeably smelling gas escaped, which 
when ignited burned with a small but intensely blue-coloured 
flame. 
* Mr. Sharpe has maintained the same opinion in the 2nd vol.|of the Man- 
chester Memoirs. See Dr. Thomson’s Outline of Heat and Elasticity, p. 198. 
t “ Quant a la valeur de elle nous est jusqu’a present tout-a-fait incon- 
nue.” — Poisson, Mec.y tom. ii. p. 652. 
