M. MEl.r,0\I O.V THE POLARIZATION OF HEAT. 



Table III. 

 Source of heat, the Jlame of a Locatelli lamp. 



339 



NAMES 



of the 



substances interposed 



before the introduction 



of the 



calorific radiation 



into the 



tourmalines. 



Calorific transmissions 



through each interposed layer and 



the same pair of tourmalines 



(No. 5 in the first table) 



in the position of the axes. 



Parallel. 



Arcs 



ofimpul- Forces, 

 sion 



Perpendicular. 



Arcs 



ofimpul 



sion. 



^ CO a> o 



' — ■£ o 



-— .a .s n 

 i2 S 5 C- 



No screen 



Glass blueish green . . . 



opake black 



Sulphate of Barytes ... 



Oil of colza 



Sulphate of Lime 



Glass uncoloured 



Ditto 



Glass coloured (red) ... 



(orange) 



• ( yellow) 



(indigo) 



— (violet).. 



0-00 

 1-93 

 1-98 

 2-60 

 8-49 

 2-71 

 1-85 

 8-27 

 1-80 

 1-87 

 1-79 

 1-83 

 1-78 

 1-81 



17-11 

 17-65 

 17-10 

 17-33 

 17-52 

 17-76 

 17-27 

 17-81 

 17--19 

 16-91 

 17-22 

 16-87 

 16-98 

 17-30 



14-84 

 15-30 

 14-83 

 15-03 

 15-19 

 15-39 

 15-08 

 15-43 

 15-16 

 14-67 

 14-93 

 14-64 

 14-73 

 15-00 



15-15 

 15-54 

 15-06 

 15-23 

 12-95 

 12-74 

 16-24 

 17-05 

 16-32 

 15-77 

 16-12 

 15-81 

 15-86 

 16-20 



13-15 

 13-49 

 13-05 

 13-21 

 12-80 

 12-63 

 14-11 

 14-79 

 14-17 

 13-69 

 14-00 

 13-73 

 13-78 

 14-06 



11-35 



11-83 



11-94 



12-07 



15-65 



17-91 



6-46 



4-17 



6-53 



6-70 



6-15 



6-20 



6-44 



6-29 



It is to be observed that the extreme limits of the variations produced 

 in the index by the interposition of the screens differ considerably less 

 than they did relatively to the pale yellow tourmalines ; a circumstance 

 which indicates a greater homogeneity in the calorific stream trans- 

 mitted by the tourmalines actually employed. Moreover, the index of 

 polarization undergoes but a very slight alteration under the influence 

 of the green and the opake-black glasses, which produced a reduction 

 of between twelve and nineteen twentieths in the direct index of the 

 table that precedes the above. The diathermancy of these green tour- 

 malines is therefore analogous to that of the green and the opake-black 

 glasses. 



As to the white, red, orange, yellow, blue, indigo, and violet glasses, 

 they diminish the index of polarization instead of leaving it in its natu- 

 ral state, as in the instance of the pale yellow tourmalines. In this 

 there is nothing that should surprise us, since the difference of diather- 

 mancy proper to the two polarizing systems causes these uncoloured and 



