the Heat extricated frorn Air by Condensation, 153 



doxical circumstance, that a correct result may sometimes be 

 obtained from erroneous premises ; but fortune has not here fa- 

 voured Mr Ivory with any such conclusion, nor saved him from 

 announcing, as the result of his investigation, a proposition 

 which, he says, " solves the problem,"" although it may not only 

 be condemned on its own evidence, but it obviously involves 

 the consequence, that air, having the temperature of 32° F., 

 can never by compression be brought to 212°, — a result noto- 

 riously at variance with observation, which has never yet disco- 

 vered a limit to the rise of temperature, — but a result, let us re- 

 collect, which supposes the absolute zero at — 448° F. When 

 would tinder kindle under the boiling point * ! Had the same 

 air been rarified only eight times, it would have been cooled 

 down to — 1228° F., or 780° below the absolute zero above men- 

 tioned. A more extravagant inconsistency cannot well be con- 

 ceived, if we except the still greater cold attending a greater ra- 

 refaction ; and yet, according to the laws of 1 825, the greatest 

 cold could never reach — 448°. 



The proposition alluded to, and which announces Mr Ivory's 

 new law, is this : " The heat extricated from air when it under- 

 goes a given condensation^ is equal to | ths of the diminution of 

 temperature required to produce the same condensation^ the pres- 

 sure being constant. 



But since ignorantia legis 7iemini excusat, I shall, for the 

 reader's edification, present him with a comparison of the laws. 

 Let a be the expansion in the volume of air at zero, for one de- 

 gree of the thermometer ; t the temperature by the common 

 scale, for the initial density ; and i the change of temperature 

 on the same scale, produced by changing the density of the air 

 in the ratio of § to unit ; or, g is the quotient of the density at 

 the end of the operation, when divided by that at the begin- 

 ning. Then the old law of condensation given in 1825 is 



l±fl (,»_:), 



• According to the experiments of M. Gay Lussac, tinder or amadou be- 

 comes ignited in air condensed into one-fifth of its bulk. But this, by the 

 new law, only produces a temperature of 32* + 144° = 176° F., or 36° under 

 the boiling point ! 



