234 
SECOND REPORT - 1832 . 
analogous to the usual influence of the wind on the barometer, 
a point not yet quite satisfactorily elucidated, and presents a 
connexion not to be lost sight of. Mr. Harris, with his usual 
diffidence, suggested it to me merely as a coincidence worthy 
of notice, not as the foundation of any hypothesis, and has per¬ 
mitted me to mention his observation here. 
The other principal oscillation strictly periodical which we 
have to notice, is one of which even the existence is hypothetical; 
I allude to the lunar atmospheric tides. It is remarkable that 
the observations most lately made, and now before us, are^of the 
most contradictory character. M. Bouvard, by his deductions 
from the observations at the Paris Observatory, has been led to 
the conclusion that the minimum pressure takes place at new 
and full moon, the maximum at the quadratures* * * § . Mr. Lub¬ 
bock, by the discussion of observations carried on for three 
years at Somerset House, concludes that the maximum takes 
place at the syzygies, the minimum at the quadratures, or pre¬ 
cisely the reverse f. M. Flaugergues, on the other hand, to 
complete the contrariety of opinion, has stated, in a memoir on 
his own observations, the maximum to take place at the last 
quadrature, and the minimum half-way between the first quad¬ 
rature and full moon J. He states the difference of height at 
l mm -48. Laplace is disposed to consider the lunar influence as 
not yet established §. On the whole, we must be content to 
leave this interesting question quite open to discussion. 
Among the variable causes which affect the barometer, we 
shall first notice the direction of the wind. Upon this point 
observations are more at one. Both the observations at Paris 
and at London, just referred to, indicate a maximum of pres¬ 
sure when the wind is N.E., decreasing in both directions of 
azimuth till it reaches a minimum between S. and S.W. This 
fact may therefore be considered quite established in this cli¬ 
mate. The difference of extreme heights amounts at Paris 
to no less than seven millimetres ; at London (from a smaller 
number of observations,) it amounts to above T ^ths of an inch, 
or nearly eight millimetres. Burckhardt, from the observa¬ 
tions of Messier, made it 5 mm, 146||. The fact of the rise 
of the barometer in this country with an east wind, is one of 
the commonest subjects of remark. It is probably in a great 
measure owing to the cold which accompanies our east winds 
* Memoires de l'Institut pour 1824. 
4 Philosophical Transactions, 1831, p. 227. 
| Bibliotheque Universelle, xl. 265. 
§ Mecanique Celeste, tom. v. Supp. p. 30. 
Jj Connaissance des Terns, 1805. 
