51 4 Dr. Schafhaeutl 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)j 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 ticith 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.] 



T^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. 



■)- " Quant a la valeur de y, elle nous est jusqu'a present tout- a- fait incon- 

 nue." — Poisson, Mec, torn. ii. p. 652. 



