1895.] on the Radiant Heat from the Moon during an Eclipse. 629 



that the difference — some 300° F. — between the lunar temperature 

 when illuminated and when dark causes a sufficient difference in the 

 power of the heat-rays to penetrate our atmosphere ? I hardly think 

 that this is a sufficient explanation. 



Fig. 9. 



This is the last eclipse which we have been able to observe. We 

 were ready for that of February last, but clouds interfered the whole 

 time, otherwise the opportunity would have been valuable for the first 

 period, and we might have carried our observations still further back 



Fig. 10. 



before the eclipse. I should have much liked to give you some 

 even imperfectly reduced results of that night's work this evening. 



I will now describe briefly the apparatus used, preparatory to a few 

 remarks on that of Professor Langley and of others, and on the results 

 of their work. 



Vol. XIV. (No. 89.) 2 u 



