upon Radiant Heat. 361 
passed through them to the thermo-electric pile. The layers are 
arranged in the order of their thickness, the thinnest coming 
first :— 
Mires Lis <hr eceans 18 bone et tees Yen atl tn cies peels el gts ae, 
Deflection after 
a passing through | Yellow glass.} Blue glass. Red glass. | Green glass. 
S the silver. 
1 10-00 100 : 42 100 : 34 100 : 27 100: 21 
2 9:91 100 : 35 100 : 34 100 : 26 100: 21 
3 781 100 : 36 100 : 36 100 : 26 100 : 23 
4 5-11 100 : 33 100 : 38 100 ; 22 100 : 25 
5 1-00 100: 31 100 : 43 100 : 20 100 : 28 
6 0:94 100: 30 100 : 43 100: 19 100 : 28 
According to this, 42 parts of every 100 which had passed 
through the thinnest layer of silver were transmitted by the yel- 
low glass; but only 33 of every 100 which had passed through 
the thickest layer. Before passing through the silver, the heat 
was far more capable of passing through the yellow glass than 
afterwards, for in the former case 63 parts out of every 100 were 
transmitted. 
Out of every 100 parts which had passed through the thin- 
nest layer of silver, 34 were transmitted by the blue glass; 
but out of every 100 which had passed through the thickest layer, 
43 were transmitted. Before passing through the silver, 38 
parts out of every 100 were transmitted by the blue glass. 
The experiments therefore show that the quantity of heat 
which passed through the yellow and red glasses diminished as 
the thickness of the layer of silver increased, while under the 
same circumstances, the quantity which passed through the blue 
and green glasses was augmented. All the experiments show 
that the properties of the heat—for example, its power of passing 
through the coloured glasses,—is changed by its passage through 
the silver, the difference increasing as the thickness of the layer 
of silver is increased. The experiments also show that the heat 
transmitted by the gold is different from that transmitted by the 
silver. 
When the heat was sent through a layer of platinum and ex- 
amined by the coloured glass, it yielded the results recorded in 
the second horizontal line of figures of the following Table. For 
the sake of comparison, the numbers obtained before the pla- 
tinum was introduced are given in the first line :— 
12 8 SE ee ee 
Yellow glass. Blue glass. Red glass. Green glass. 
100 :59 100: 41 100: 46 100 : 20 
100: 61 100 : 44 100 : 46 100 ; 22 
