Heat across Layers of Gas. 435 



most satisfactory accordance with the theory presented in this 

 memoir. 



13. If we suppose the shaded portions of the ordinates in 

 fig. 3 to be moved vertically downwards till they abut upon a 

 horizontal axis of abscissas, we shall obtain the curve in fig. 5, 













^^ 



■ ' -/ff 







1 -. 











II 



Ml ! !l 



1 



1 



1 



SB— 



A: 







iO 2\0 zp 4p ^0 m '"'■ jp Ttn 

 \ i i \ : V \ ■■ / i •■■ 



sions 



^ 



the ordinates of which represent the rate at which heat escaped 

 by penetration in De la Provostaye and Desains's cylinder, 

 separated from the effects of radiation and convection. 



We can only compare this figure in a 

 very general way with the formula given 

 above for the escape of heat by penetra- 

 tion, 



VIZ. 



dt 



V<rp, 





(S) 



because too little is known of V, pi^ and 

 A^i to enable us to plot down a curve 

 from this expression*. But we can, at 

 all events, see that Y will be only mode- 

 rately affected by alterations of tension, 

 that pi will vary nearly as the tension, 

 and that as the tension is diminished A^i 

 will gradually rise from to a value 

 w^hich is nearly 4(^1 — ^2)- Hence the 

 curve must be one somewhat like that of 

 fig. Gf, whose ordinates first rise gradu- 



* Just as the parabolic curve of convection 

 could not have been plotted down from equation 

 (0> § ^j owing to the vagueness of some of the 

 quantities which appear in it, viz. Q, v, and A^. 



t In fig. 6, OB is intended to represent a 



a Q 



portion of the curve t/=V(rpi^-^-^^, and On A. 



the result of shortening its ordinates in the ratio 

 A<9i 



^i|u]jj] lj l|[ il l ll H^^ 



1(^1 -^a) 



2F3 



