Mr. Tredgokl on the laleJit Heat of Vapours. 27 Y 



the labours and discoveries of Mr. Herapath " in other parts 

 of his writings." Nothing could be further from the truth 

 than such a charge. The majority of Mr. H.'s writings have 

 not been upon subjects in which the demonstx'ation of the 

 binomial, or even the truth of the binomial, is at all con- 

 cerned. I have objected to a very small number of his me- 

 thods of demonstration, but have not in a solitary instance ob- 

 jected to a single mathematical fact to which he lays claim. 

 As well might P. Q. charge me with denying the truth of the 

 binomial theorem, as with involving in the ruins of a single 

 demonstration most of the labours of Mr. Herapath's life ! 



Bristol, Oct. 12, 1825. 



Erratum. — In line 14 of my former paper (p. 115), yb/- "that perfect 

 one of all," read " that most perfect one of all." 



XLII. Correction in Dr. Ure's Paper on the latent Heat of 

 Vapours. By T. Tredgold, Esq. 



To Richard Taylor, Esq. Sfc. 

 Sir, 



T N Dr. Ure's )iaper on the latent heat of vapours in the 

 -*• Philosophical Transactions for 1818 (see Phil. Mag. vol. liii. 

 p. 193) a considerable error in the mode of calculating the re- 

 sults of the experiments has not been noticed. When it is 

 coi-rected, we have for the latent heat of steam, 888° instead of 

 967°, for that of alcohol 355-1° instead of 442°, &c. The 

 error occurs in the second operation. " From 42*5° to 212° 

 there are 169*5°; one half of which = 84*75°, or in round 

 numbers 84°, is the rise of temperature which would be pro- 

 duced by adding to water at 42*5° its own weight of boiling 

 water ; and jf j 7 = 0*5 2* is the elevation which 200 grs. would 

 occasion on 32340 grains." But the 200 grains has been 

 added to 200 grs. to reduce its temperature to 84° of excess : 

 hence, either this reduction should not have been made, or 

 84 should be divided by -ifg^-^ = 80*85 instead of 161*7. 



Calculating by the formula for mixed fluids ( Playfair's Nat. 

 Phil. vol. i. art. 3 17) we have 888*05 = the latent heat of steam, 

 when we suppose, as Dr. Ure has done, that there is no loss 

 of heat in the operation, and that the specific heat of water is 

 the same in the whole range of temperature from 42*5 to 212. 



Perhaps the notice of these errors in your Journal will lead 

 to an investigation of this interesting subject. 



I am, sir, your most obedient servant, 

 16, Grove Place, Lisson Urovc, Oct. 18, 1825. Thomas Tredgold. 



XLIII. Me- 



