AS AFFECTED BY THE MOON’S DECLINATION. 
443 
In my former paper, I exhibited likewise a set of averages upon the whole solar year , 
from 1815 to 1832, in which the yearly mean pressure increases to the middle of a 
cycle of eighteen years, and then decreases with great regularity to its former amount. 
I have inserted here a similar calculation, but with an opposite result; which shows 
the pressure decreasing from year to year, and then recovering in some measure its 
former level : but this, for reasons already given, comes out less regular and symme- 
trical than the other. I have no doubt that, when we shall have prosecuted further 
the comparison of the yearly mean pressures with the temperatures, there will be 
found a contrast between the two halves of a cycle as evident as that I have shown 
to exist in those of the cycle of temperature. 
In the long average, 181 5 to 1841, we have, — 1, a half cycle cold ; 2, a half cycle warm ; 
3, a half cycle cold ; the result of which must needs show a preponderance of the 
effect of cold. But let the temperatures balance, as in the cycle 1815-32, we have 
then — 1, coming north 29*831 0 in. ; 2, north 29*8260 in. ; 3, going south 29*8171 in. ; 
4, south 29*8056 in. Again, in the balanced cycle 1824-41, we have for the four 
respectively, — 1, coming north 29*7816 in. ; 2, north 29*7601 in.; 3, going south 
29*7522 in. ; 4, south 29*7586 in. The results of this last average are subject in some 
degree to the effect of a more northerly site. Without presuming to determine even 
that latitude has such an effect in a space of less than three degrees, I have thought 
it right to place these data in the hands of the Fellows, that future students may have 
the opportunity (now that we have begun to distinguish between the various causes 
affecting the gravity of the atmosphere) of comparing (with much trouble saved) the 
actual differences which obtain in it, under different positions of the planet; and of 
analysing, with the help of the register whence they are derived, a great mass of ob- 
servations tending to throw light on the nascent science of meteorology. 
I have to acknowledge, in concluding this paper, my obligations to my young* 
friend^ Cornelius Hanbury, who made for me the preliminary calculations upon the 
register with much care, and, I am satisfied, with the required accuracy. 
L. II. 
Achworth, October 25, 1844. 
3 m 2 
