REPORT ON METEOROLOGY. 
251 
At Geneva by a mean of 32 years the annual fall of rain is 
.‘107 inches ; at the Grand St. Bernard by a mean of 12 years 
it is 60*05 inches. 
The variation in the amount of rain with the seasons follows 
in a great measure the same law, founded on hygrometric prin¬ 
ciples, which causes the difference in different latitudes. The 
greatest quantity falls in summer, the least in winter. The influ¬ 
ence of the lunar periods has also met with some attention. The 
popular belief of the influence of the moon upon the weather is 
probably too strong and too universal to be totally without foun¬ 
dation. At one time I attended a good deal to the subject, and 
my observations led me to believe that there was some real con¬ 
nexion between the lunar phases and the weather. The old 
writings of La Cotte and Toaldo contain some curious observa¬ 
tions on this subject, which has more lately been resumed by 
M. Flaugergues, who has observed the weather at Vivierswith 
great assiduity for a quarter of a century. He has marked the 
number of rainy days corresponding to the lunar phases, and he 
finds them at a maximum at the first quadrature, and at a mini¬ 
mum at the last *. This agrees pretty nearly with his corre¬ 
sponding observations on the height of the barometer which 
we have already recorded. 
A similar question to that which has been put in every other 
branch of Meteorology, whether there is any secular variation, 
—has been asked in the case of rain ; and we are quite as unable 
as in the other instances to afford any satisfactory reply to it. 
There are several causes which may tend to change the amount 
of rain on a particular spot without forming part of any general 
law; among such changes will be found the destruction or the 
planting of forests, the inclosure and drainage of land, and the 
increase of habitations. M. Arago has shown f that the fall of 
rain at Paris has not altered sensibly for 130 years; and in order 
to show that the conclusion drawn by M, Flaugergues at Viviers, 
that the amount of rain is on the increase, cannot be a general 
one, he has quoted the case of Marseilles, where the amount of 
rain appears to have undergone a striking decrease in 50 years. 
M. Arago justly observes that it is very difficult to know how 
many years of observation are necessary to get a mean value of 
the fall of rain, the amount being extremely variable: thus at 
Milan, where an increase of rain has been thought to be de¬ 
cidedly proved by observations for 54 years, the extremes of 
the annual results between 1791 and 1817 were 24*7 and 58*9 
inches 
* Bibliotheque Universelle, xl. 283. 
X Annuaire, 1825, p. 155. 
f Annuaire, 1824. 
