366 Prof. Knoblauch on the Influence of Metals 
Yellow glass. Blue glass. Red glass. Green glass. 
Gold. cecsccss.. eee 100 : 69 100 : 37 100 : 56 100: 17 
@Opper caesa<..esece 100 : 67 100 : 38 100: 55 100: 16 
Brasspised...-0cthy= <a 100: 66 100 : 37 100 : 53 100: 18 
Unreflected heat... 100 : 61 100 : 38 100 : 52 100: 18 
According to this, the heat reflected from copper and brass is 
also more copiously transmitted by the yellow glass; but the 
augmentation is not so great as in the case of gold. In the case 
of the red glass, the quantities transmitted from gold and copper 
are nearly equal ; but with brass no sensible difference is observed 
between the reflected and unreflected heat. Here also, as in the 
former instance, the blue and green glasses show no difference 
between the reflected and unreflected rays. 
A similar series of experiments was made with silver, mercury, 
and German silver. Each had a reugh surface; the mercury 
was rubbed upon copper, and had a milky appearance. The 
following Table contains the results of the experiments :— 
Yellow glass. Blue glass. Red glass. Green glass. 
Silver! Ji. esscsecscee 100 : 72 100 : 38 100: 55 100: 17 
Mercury .....eeeeee 100 : 72 100: 38 100:: 55 100: 18 
German silver...... 100 : 66 100 : 38 100 : 52 100:18 
Unreflected heat...) 100: 66 100 : 38 100:51 100: 18 
ee ee ee ee 
The rays reflected from mercury exhibit, according to this, 
quite the same deportment as those reflected from silver ; while 
those reflected from German silver are not to be distinguished 
from those coming directly from the sun. 
The heat reflected from lead, tin, and alloys of both metals 
gave the following values :— 
Yellow glass. Blue glass. Red glass. Green glass. 
100 : 64 100 : 42 100: 51 100: 15 
100 : 64 100 : 42 100: 51 100: 15 
100 : 64 100 : 42 100: 51 100:15 
Unreflected heat ...} 100: 64 100 : 42 100; 51 100: 15 
The reflexion from these bodies has, according to this Table, 
no influence on the transmissibility of the heat through the 
coloured glasses. 
Experiments with rough surfaces of zine, iron, and black sheet- 
iron, also showed that no sensible difference existed between the 
heat reflected from them and the direct heat. 
The results of all the observations on reflected heat are 
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