9 
POPULAR SCIENCE REVIEW. 
The difference thus shown is so small that it might be as- 
cribed to accident, did not other and subsequent comparisons in 
a measure corroborate it. Buys Ballot tabulated the result of 
1 18 years’ observations, summing the temperatures for each day 
of the moon’s age, and his result also showed a maximum of 
temperature at about the day of full moon, strictly speaking, a 
few days after.* But Mr. Park Harrison, who has classified 
several series of observations made in recent years, arrives at a 
conclusion almost the opposite of those of Toaldo and Buys 
Ballot From readings of the thermometer at Greenwich, 
between 1841-1847 and 1856-1864, at Oxford between 1856- 
1864, and at Berlin between 1820-1855, he shows that the 
maximum occurs six or seven days after new moon and the 
minimum about four days after full. Mr. Harrison’s curves 
laid down from his tabulation are remarkably consistent, and 
the difference between the maximum and minimum is very 
decidedly marked, for it amounts, from the average of all the 
series, to 2*5° Fahrenheit ; that is to say, the whole heating 
effect of the moon upon Europe at first quarter is in excess of 
that at last quarter by two-and-a-half degrees.f Professor 
Loomis, using five years’ observations made at Philadelphia for 
a similar investigation, arrived at a result strikingly coincident 
with this of Mr. Park Harrison’s.J How are we to explain the 
discordance between Buys Ballot’s conclusion and these ? It 
may be that it is due to some slight difference in the grouping 
of the observations ; or it may be that the periods covered by 
Harrison’s and Loomis’s groups are not sufficiently long to give 
a reliable result. Buys Ballot divided his 118 years into twelve- 
year periods, and if some of these had been taken separately, it 
is apparent from an inspection of his tables that they would 
have given evidence differing in some degree from that afforded 
by the whole number of years. 
By either conclusion, however, the fact of lunar influence on 
temperature is pretty well established. Mr. Harrison’s, it is 
true, appears paradoxical, for he makes the new and practically 
cold moon warm us, and the full and presumably hot moon cool 
us. His explanation, however, is philosophical : it involves a 
consideration that was put forth by Buys Ballot twenty years 
ago, to account in some measure for the small amount of lunar 
heat evidenced by thermometric investigations in proportion to 
that which we may suppose the full moon to shed earthwards. 
It is an accepted conclusion that the heat is of two qualities — 
• Buys Ballot, “ Changement* periodiques de Temperature, dependants de 
la Nature, du Soleil, et de la Rune.” Utrecht, 1847, p. 70. 
t “ Monthly Notices of Roy. Astron. Soc. t ” vol. xxviii. p. 39. 
t “ Proceedings of American Association for the Advancement of Science,” 
