190 



PROFESSOR FORBES'S RESEARCHES ON HEAT. 



41. The numbers from whicli these projections are derived are contained in 

 the following Table.* 



Source of Heat. 



Depolarizing Plate. 





Values of" ' 







0, 





Argand-Lamp, . . . 



No. 1. 



repeated. 





.18, .82, 1.18, &c. 





No. 2. 



li=-^^ 



.30, .70, 1.30, &c. 





No. 3. 



^■f„ = .629 

 8.38 



.29, .71, 1.29, &c. 





No. 2. + No. 3. 



!! = ■«'« 



.21, .79, 1.21, &c. 





No. 6. 



m = •^^"l 









It = -298) 

 4.83 



.185, 815, 1.186, &c. 





repeated. 





Incandescent Platinum, 



No. 1. 



11-:= ■^«* 



.17, .83, 1.17, &c. 





repeated. 



;^=-^» 



.166, .835, 1.166, &c. 





No. 2. 



?A; = .e3s 



.30, .70, 1.30, &c. 





No. 3. 



S=-'« 



.335, .665, 1.336, &c. 





No. 4. 



III = -W^ 



.35, .65, 1.35, &c. 





No. 2. + No. 3. 



iS = -=- 



.19, .81, 1.19, &c. 





No. 6. 



^ = -^'^ 



.16, .85, 1.15, &c. 



Dark Hot Brass, 



No. 1. 



;iS=-* 



.17, .83, 1.17, &c. 





No. 2. 



iii=-7^ 



.34, .66, 1.34, &c. 





No. 3. 



3.64 



3.98 = •»!« 



.41, .69, 1.41, &c. 





No. 2. + No. 3. 



IS=-- 



.186, .816, 1.186, &c. 





No. 6. 



i:--^ 



.116, .885, 1.116, &c. 



42. When we examine the projected interpolating lines of Plate XI, which an 

 attentive inspection wiU shew to have been laid down Avith the greatest care,f we 

 are struck by the remarkable coincidence which obtains between them ; a result so 

 far contrary to what I expected, that it shews that by this method we cannot hope 



* Most of the experiments on incandescent platinum were made early in 1837, the remainder during 

 the winter 1837-8. 



I The interpolating line for Incandescent Platinum is in the engraving placed at rather too high 

 an angle. 



