1834.] 6n Atmospherical Phenomena. 355 



the atmospheric currents being acted on by the attractive force of the 

 moon*. The barometer is next alluded to, but the circumstance of the 

 specific gravity of air being diminished by its being mixed with aqueous 

 vapour, must tend to render very uncertain any deductions from in- 

 equalities of pressure alone. 



Medical men will be able to judge, whether the recurrence of a very 

 hio-h dew-point, or in other words, of great moisture, at certain fixed 

 days in the lunar period, is sufficient to account for the recurrence of 

 certain diseases, in the manner they have been observed to do since 

 the earliest ages. I have now merely to add the several tables alluded 

 to in the text, of rain-falls, dew-points, and barometric heights. 



I subjoin a table of the most remarkable storms and falls of rain, 

 which, whatever may be thought of the theoretical suggestions, I hope 

 will be of use. 



[We put every confidence in the tables and in the abstracts of them drawn upby our 

 correspondent, but we regret that in calculating some of them he should have selected 

 tLose columns of the meteorological registers, which were perhapsthe most liable to 

 irregularities. At the hour of sunrise, for instance, the mercury of the barometer is 

 in motion : the chance of punctuality in the observer is less (we allude here to the 

 registers of the Surveyor General's Office, where the observer did not reside on the 

 premises) ; and the light for reading off is bad. Again, at that hour the depres- 

 sion of the wet bulb thermometer is at a minimum, and least trust-worthy for 

 shewing the hygrometric effects of aerial currents, which are also at that hour 

 generally lulled and quiescent. The aqueous tension calculated from the depres- 

 sions, or if that be too troublesome, the indications of the hair hygrometer, which is 

 not affected by heat, would best answer the purpose desired. But we would venture 

 to suggest that the barometer alone is sufficient, particularly if observed at its hours 

 of rest" its maximum or minimum at 10 a. m. or 4p m. to point out the lunar influence 

 if perceptible, on the atmosphere : for its indications are alike affected by the direc- 

 tion of the aerial currents, the moisture present, and the diminution of gravity :— 

 besides which its march in other respects is so regular in these latitudes, that upon 

 a long series of averages very small anomalies ought to be discoverable. It will 

 be seen, from the proceedings of the Asiatic Society on the 2nd July, that M. 

 Arago has applied through the French Government for copies of all meteorologi- 

 cal registers kept in Calcutta, probably with a view of solving this very question of 

 lunar influence :— The registers have been furnished, and we shall take care to add 

 a copy of the present laborious and useful analysis.— Ed.] 



* Rain falls most abundantly about the second octant, which also agrees with 

 our selection of the fifth day after as a maximum. 



