8S8 Mr. J. Snart on the Quadrature of the Circle. 



Supposing this ratio constant for vapour as well as for dry air, 

 its value is very different in the two fluids, and cannot there- 

 fore be constant in moist air, particularly if the vapour in the 

 air be considerable. Hence the fornuilae we have given in 

 $ I., being founded on the invariability of the ratio in ques- 

 tion, will not apply at the same time to simple gases and mix- 

 tures of gases and vapours. 



Addition to the preceding Memoir by M. Poisson. 

 During the printing of this memoir M. Clement has com- 

 municated to me the result of a new experiment on the tem- 

 perature of vapour under a very high pressure. According 

 to this experiment, the pressure of aqueous vapour, in the 

 state of saturation at the temperature of 215° centigrade, is 

 35 atmospheres. From these data equation (10) gives 



Q=659; 

 so that the invariability of the quantity Q appears still to 

 hold good very nearly under this high temperature. Never- 

 theless, we cannot suppose that the caloric Q is rigorously in- 

 variable; for, wei'e this the case, our equation (9) would bring 

 out 54 atmospheres for the maximum pressure of vapour at 

 215°, whereas experiment gives only 35 atmospheres. 



LXVIII. Quadrature of the Circle; and. Proportion of the 

 Diameter to the Circumference ; containing some Observatio?is 

 on its Perimeter and Area, tending to demonstrate the utter 

 Impossibility of ever obtaining a perfect Solution of these de- 

 lusive Problems: together i&ith the true and. ONLY Cause of 

 the constant Failure of all Attempts to effect it. To which is 

 added, a simple and easy Process of estimciting the most use- 

 fid Properties of the Sphere 4'c. in Mefisuration. By Mr. 

 John Snart.* 



To the Editors of the Philosophical Magazine and Journal. 



/CONSIDERING the sterling talents and very high capa- 

 ^-^ bilities of many of the speculators on these mathematical 

 desiderata, it is truly astonishing that none of them ever 

 appear to have penetrated the true cause of their continual 

 disappointment ; but, as if they were fully persuaded of the 

 entire practicability of the thing, they have all confidently per- 

 severed to obtain a still nearer and nearer approximation, 

 * Communicated by the Author. 



(which 



