624 



The Earl of Bosse 



[May 31, 



would occur appreciably later than the time of Full Moon,* but the 

 phase-curve did not indicate this ; on the contrary, whether from 

 some accidental errors or from some real though unexpected cause, 

 it showed a maximum at about 10 hours before Full Moon. 



Slide 1 will now be thrown upon the screen, in which the observed 

 phase-curve is compared with Zollner's curve for light, the latter 

 being much steeper towards the maximum near Full Moon. Zollner's 

 curve agrees more nearly with that calculated for a sphere covered 



Fig. 



with meridional corrugations whose sides are inclined 52° from the 

 surface than with the smooth sphere assumed by Lambert and shown 

 in Slide 2. In both cases the surfaces are assumed to be " matt," or 

 free from polish. 



In Slide 3 the total heat-curve is compared with that of heat 

 through glass. Slide 4 compares the heat through glass with 

 Zollner's light-curve, and it will be seen, as might be expected, that 



* If we compare these results with analogous cases on the earth, we find that 

 a very much longer time is required before the air temperature, aDd with it more 

 or less that of the earth's surface, arrives at the final temperature due to the sun's 

 radiation at the time. The maxima and minima of temperature are generally 

 three weeks later respectively than the summer and winter solstices, and tLe 

 hottest time of the day is generally about two hours after noon. Again, the fall 

 of temperature during an eclipse of the sun, though observations are very con- 

 flicting, would appear to be from 7° to 10° only. During the eclipse of July 1878, 

 radiation thermometers gave a depression of 10°, 22|°, 32° and 42°, but this is 

 far short of the depression of temperature of the lunar surface, 200°, if the surface 

 has the same radiating power as lamp-black, but probably in reality considerably 

 greater. 



