490 



Prof. C. V. Boys. 

 Fig. 4. 



[Apr. 24 



Lord Rosse obtained for the full moon, using the 3-foot telescope and 

 a very superior thernio-j unction of his own design.* The remarkable 

 symmetry of the curve for the full moon at first rather puzzled me, 

 as I expected that the side that had been baked by the snn for from 

 7 to 14 days would be hotter than the side that had only been lighted 

 up for from to 7 days. However, if we consider that soil of any kind 

 is so bad a conductor that it would acquire its final surface tem- 

 perature in perhaps an hour or less, that is,. if not protected by an 

 atmospheric blanket, the symmetry of temperature is nothing more 

 than should be expected. Lord Rosse's experimentsf on the heat of 

 the eclipsed moon fully bear this out. 



September 20th. Observed the moon on the horizon, deep red, limb 

 ill defined, and cloud bands across, looking like the belts of Jupiter. 

 A series of readings were taken, but not at exactly ten-second in- 

 tervals. The deflection 'was greatest about the middle, where it reached 

 15 mm. Four minutes later (7 2 p.m.) the deflection in the middle 

 amounted to 40 mm. The four curves, fig. 5, were taken later, as indi- 

 cated by the increasing altitude. Though the later ones especially 

 were much disturbed by wind, they well show the diminishing absorp- 

 tion by the atmosphere as the moon rose in the sky. Observations later 



* ' Phil. Trans.,' vol. 163 (1873), p. 615. 

 f ' Eoy. Dublin Soc. Trans.,' 1885, p. 321. 



