1895.] on the Badiant Heat from the Moon during an Eclipse. 623 



I also showed that we had been able by means of a long series 

 of determinations, continued on different nights, through considerable 

 increases and decreases of altitude, to determine with considerable 

 accuracy what may be called the extinction curve for heat with 

 decreasing altitude ; probably as completely as Seidel, at Munich, 

 had deduced that for light from his photometrical observations on 

 stars. 



As the phase-curve descended on each side almost to zero on 

 approaching New Moon, it was clear that little or none of the heat 



, Fig. 2. 



we were measuring came from the interior of the Moon. It was heat 

 derived directly from the Sun. 



Some series of determinations were then made alternately with 

 a sheet of glass interposed between the large speculum (of the 

 telescope) and the apparatus and with the glass removed, and from 

 the fact that from 8 to 17 per cent, of the heat (being greatest towards 

 Full Moon) was transmitted by the glass, while some 90 per cent, of 

 the sun's rays passed through the same sheet of glass, it was, we 

 think, clearly established that the heat, which we had already con- 

 cluded, as stated above, to be directly derived from the Sun was not 

 reflected sun-heat, but heat absorbed and afterwards emitted by the 

 lunar surface. 



It might, perhaps, have been expected that, as is more largely 

 the case on the Earth, the highest temperature of the lunar surface 



