M. MELLONI ON THE POLARIZATION OF HEAT. 
335 
Taste Il. Source of Heat, flame of a Locatelli lamp. 
NAMES 
of the 
substances interposed 
before the introduction 
of the 
calorific radiation 
into the 
tourmalines. 
No Sereen ... ..:..--s2025 
Glass colourless 
coloured (red) ... 
orange) 
yellow) 
-(blue)... 
(indigo) 
—oo (violet) 
Glass coloured (bluish 
eee see eee eceves 
eee eee ees 
CR aeons 
Sulphate of barytes .. 
of lime 
Oil of colza 
Tartrate of potash and 
soda 
eee eer eesseeece 
ee cee cress see eseses 
salt T 
pee ere ece ces cece 
tartaric acid 
ILLOY Gaccruses crates 
Water (distilled) 
eee cecone 
eee ces 
Thickness of the layers 
formed by these substances, 
reckoned in millimetres. 
Ditto 
Alum 
Peewee ses ses ses cesces 
Calorific transmissions 
through each interposed layer, and 
the same pair of tourmalines 
(No. 9 of the preceding table) 
in the position of the axes. 
ee —_ 
Parallel. Perpendicular. 
FS OE 
Arcs Ares 
ofimpul- Forces. jof impul-| Forces. 
sion. sion. 
17-37| 15-06 | 13-47 | 11-76 
17:93 | 15°53 | 13°94) 12°15 
16°75 | 14°54 | 13°04) 11°40 
17-21 | 14°93 | 13°31 | 11°66 
17°83 | 15°45 | 13°84) 12:07 
17°59 | 15°24 | 13°66} 11-92 
17°29 | 14°99 | 13°44] 11°74 
16°81 | 14°59 | 13°02} 11°39 
16°99 | 14°74 | 15°95 | 13°86 
17°32} 15°02 | 16°85) 14°62 
17°55 | 15°21 | 16°76} 14°55 
17:80] 15°42 | 17°52} 15°19 
17:10 | 14°83 | 13°18 | 11°52 
16°95 | 14°71 | 10°54} 9°18 
16°97 | 14°72 | 10°40} 9°05 
17°39| 15°08} 9°49) 8°26 
17-49| 15:16} 5°78} 5°06 
17°56 | 15°22| 5°81) 5:08 
17°39 | 15°03 | 5°76| 5°04 
16°96 | 14°72 | 10°76} 9°38 
16°77 | 14°55 | 5°54) 4°85 
17°20} 14°92] 10°91] 9°50 
17°23 | 14°94] 8°35| 7°29 
16°98 | 14°73 | 0°58} 0°52 
Indices of polarization in hundredth 
parts of the quantity of heat trans- 
mitted by the system of the three 
plates when the axes of the tourma- 
lines are parallel. 
21°91 
21°79 
D157 
21°90 
21°89 
21°78 
21°68 
21°92 
5°95 
2°76 
4°35 
1°51 
22°30 
37°63 
38°50 
45°21 
66°60 
66°63 
66°59 
36°31 
66°67 
36°27 
51°23 
95°81 
* The physical characters of this species of glass, which acts so differently from 
the other species of coloured glass in all the phenomena of calorific absorption, 
are, Ist, its intercepting almost totally the rays which pass through alum; 2nd 
its entirely absorbing the red rays of the solar spectrum. I have already stated 
that their coloration is produced almost entirely by the oxide of copper. 
+ The temperature of these different saturated solutions was about 15°. 
