MADE AT THE APARTMENTS OF THE ROYAL SOCIETY. 
227 
The following Table results from Table VI. of M. Bouvard, (p. 316,) reduced 
to English feet. 
Variation of Barometer 
from 
mean. 
9 A.M. 
3 P.M. 
inch. 
inch. 
Day of the Syzygy 
— .004 
-.008 
First day after the Syzygv 
-.010 
—.006 
Second day after the Syzygy 
-.013 
-.009 
Second day before Quadrature .... 
+ .008 
+ .005 
First day before Quadrature 
+ .024 
+ .032 
Day of the Quadrature 
+ .025 
+ .017 
First dav after the Quadrature .... 
— 002 
—.001 
Second day after the Quadrature . . 
-.000 
+ .012 
Second day before the Syzygy .... 
-.019 
— .018 
First day before the Syzygy 
-.009 
-.019 
Mean height 
29-781 
29-748 
The results afforded by the observations at Somerset House differ widely 
from those above obtained by M. Bouvard from the observations at the Paris 
Observatory ; according to the former, the barometer is highest at new and full 
moon and lowest at quadrature ; according to the latter, the contrary is the 
case. 
The extent of the fluctuations of the barometer due to the moon according 
to the former is about .08 or nearly yoth of an inch, according to the latter 
only *05 or ^th of an inch. 
They agree in this, that the fluctuations take place nearly in the same 
manner in the morning and in the afternoon ; whence it follows, that the period 
of the principal inequality of the height of the barometer due to the action of 
the moon is not the same as that of the ocean ; for if it were so, as the obser- 
vations are made at a distance of six hours, the maximum in the morning 
would correspond to the minimum in the afternoon. 
Laplace enumerates among the most important causes of the fluctuation of 
the pressure of the atmosphere, the rising and falling of the ocean due to the 
action of the sun and moon, the ocean serving as the basis or support of the 
atmosphere. But with that deference which is due to the authority of so great 
2 g 2 
