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of the lunation, when the moon’s crust turned towards the 
earth is coldest ; and a minimum mean temperature some 
time after full moon, when the same crust has been exposed 
for several days to intense radiation from the sun. It does 
not appear that any other period than that of the moon’s 
synodical revolution was tried ; nor is any allusion made to 
the temperature period which, as Nervander and Buys 
Ballot showed many years ago, depends apparently upon 
the sun’s geocentric rotation on his axis. The existence of 
both these periods has however been questioned. Thus 
Buys Ballot on tabulating a series of 70 years’ mean daily 
temperatures according to the moon’s age found that the 
highest temperatures occurred during the seven days after 
full moon, or precisely during that part of the lunar period 
in which, according to Mr. Harrison’s results, the tempera- 
ture is at a minimum ; and the Astronomer Royal discussing 
the observations of temperature made at Greenwich from 
the 2nd of June, 1848, to the end of 1853, with reference to 
the period of the sun’s geocentric rotation on his axis, 
obtained a series of numbers “ which did not appear to sup- 
port the hypothesis that there is any certain inequality of 
temperature depending on the meridian of the sun which is 
turned towards the earth.” In an inquiry of this nature it 
is, however, manifestly very undesirable to rely upon ob- 
servations taken during the same series of years at places 
so near each other as Greenwich and Oxford, or upon those 
taken at places far apart, but in different years. The 
general agreement between the results of the Berlin ob- 
servations in 1820 to 1835, and those at Oxford in 1856 to 
1864, as given by Mr. Harrison is, of itself, no proof that 
the temperature of the earth’s atmosphere is sensibly 
affected by the moon. This agreement may, and indeed 
does, arise from causes altogether independent of any in- 
fluence of the moon. In a paper which I communicated to 
this Society in March, 1864, “ On Periodic Changes in the 
