MADE AT THE APARTMENTS OF THE ROYAL SOCIETY. 
225 
may be applied to this or any other useful purpose, except that of serving at 
the time to prognosticate the weather, or but imperfectly to determine the cor- 
rection due to the direction of the wind. 
I was therefore obliged to confine myself to the years 1827, 1828, and 
1829. The method which I have adopted with respect to these aerial tides 
is similar to that which I have used in order to determine the phenomena of 
the tides in the river Thames, and consists in classifying all the heights of the 
barometer, and taking their mean, which correspond to a particular age of 
the moon, defined by the circumstance of her transit taking place in a given 
half-hour of the day. Thus all the days in the years 1827, 1828, and 1829, 
were found when the moon passed the meridian between 12 and half past 12, 
and the mean of the transits taken, which of course is nearly a quarter past 1 2 ; 
the heights of the barometer were then taken on the same days, and the mean 
taken ; and thus all the transits of the moon which occurred during the years 
1827, 1828, and 1829, were taken, and the corresponding observed heights of 
the barometer selected and compared with them. The height of the attached 
thermometer was also taken, and the mean height of the barometer corrected 
afterwards by the mean height of the attached thermometer, so as to reduce it 
to 32° Fahr. 
Although the transits of the moon were at first classed for every half-hour, 
I afterwards combined them for every hour, in order to make use of a greater 
number of observations in obtaining results. The mean transit thus found, 
scarcely differed from the half-hour, which is therefore taken as the time of 
the moon’s transit in the following Table, in which the results are exhibited. 
2 G 
MDCCCXXXI. 
