320 Royal Society. 



The part which tails on the earth 



= K.f 5 ^{(>-<Ocose-t- sine} sin e.de 



Jo 



= _X \ — 7T . versin (1° 55')+ ^ _ , v u . . '- — fsm(l°o5) \ 



4 [ o9'9u4 J 



= — . E suppose ; 



therefore (if we may be allowed the expression) 



sun-heat 13*55 x 3tt 79,000/ -v. /A 



moon-heat = E = ~ (q™m proximfc). . . . (d) 



In the above, the proportion between the areas of surface pre- 

 sented by the moon and earth to the sun is taken =13*55, and the 

 angle subtended by the earth at the moon =1° 55'. 



The value of the readings of the galvanometer was determined by 

 comparison with those obtained by using a vessel of hot water coated 

 with shellac and lampblack varnish as a source of heat. The vessel 

 was of tin, circular, and subtended the same angle at the small con- 

 cave reflectors as the large mirror of the telescope. It was thus 

 found that (the radiating power of the moon being supposed equal 

 to that of the lampblack surface and the earth's atmosphere not to 

 influence the result) a deviation of 90 for full moon appears to in- 

 dicate an elevation of temperature through 500° Fahr.* In deducing 

 this result allowance has been made for the imperfect absorption 

 of the sun's rays by the lunar surface. 



In the present imperfect state of these observations it would be 

 premature to discuss them at greater length ; but as some months 

 must elapse before any more complete series can be obtained, and 

 the present results are sufficient to show conclusively that the moon's 

 heat is capable of being detected with certainty by the thermopile, I 

 have thought it best to send this account to the Royal Society ; and 

 I shall be most happy to receive suggestions as to improvements in 

 the method of working, and as to the direction in which it may be 

 most desirable to carry on future experiments. 



GEOLOGICAL SOCIETY. 



[Continued from p. 243.] 



February 10th, 1869.— Prof. T. H. Huxley, LL.D., F.K.S., 



President, in the Chair. 

 The following papers were read : — 



* This may seem a very large rise of temperature ; but it is quite in accordance 

 with the views of Sir John Herschel on the subject (Outlines of Astronomy, 

 section 432 and preceding sections), where he says that, in consequence of the long 

 period of rotation of the moon on its axis, and still more the absence of an atmo- 

 sphere, " The climate of the moon must be most extraordinary, the alternation 

 being that of unmitigated and burning sunshine, fiercer than that of an equatorial 

 noon, and the keenest severity of frost, far exceeding that of our polar winters, 

 for an equal time." And again, " . . . . the surface oi the full moon exposed to 

 us must necessarily be very much heated, possibly to a degree much exceeding 

 that of boiling water." 



