I have noticed this because, by supposing a similar anomaly in the case of the tides of the air, we may explain why the ninth day before new moon has a less proportionate rain-fall in summer, (when the moon at that age has usually south declination,) than it has in winter, when the moon at that age has north declination; and vice versâ, why the fifth day after new moon has a greater excess of rain-fall in summer, when its moon has north declination, than in winter, when its moon has south declination. Were the lunar theory correct, the excess in one tide, owing to the moon's declination, would be compensated by the defect in the opposite tide. Similar anomalies commonly prevail. Thus we read, "At Brest when the moon has great declination the superior tide may be three times greater than the succeeding, or inferior tide; but the fact is, they differ very little. M. LA PLACE says, they do not differ at all."-(Mechan. Philos. iii. 365.) But to return to the matter before us. Having made out a table of the dew-points at Calcutta for 1832, I selected the heights of the same days as are stated in Mr. NOTON's paper of the Bombay tides, and took the average in the same way. Comparing the times of new and full, the numbers were But as the heating power of the sun (as the year advances) must affect the current of air, and consequently the dew-points, whereas the tides of the sea are affected wholly by the attractive forces of the sun and moon, no correct comparison can be drawn between them. Thus the first item under "Full" is 46.3, which is less than the item under New," 53.1. But it may be said, that the time of the average 46.3, is near 15 days earlier than that of the corresponding average 531; that as the dew-points increase with the year from January to June, owing to the heat principally, the item under “Full” (46-3) is less than that under “New” (53·1), owing to its being so much earlier, and consequently less affected by the heat of the sun. To obviate this difficulty, we may remark that, if the first item under “ Full” is 15 days earlier than that under "New," the next item below it (62-1) is fifteen days later; the mean between them therefore would correct any discrepancy arising from increase or decrease of heat in either case. 66 Proceeding in this manner, i. e. taking the mean of each number in succession with the one below it, in the column headed" Full,” the comparison becomes as follows. I have placed the Bombay tides of the same period in the same line, that the agreement may be more apparent. Disclaiming then the wish of speaking positively on a subject where no decisive proof has been adduced, we may yet be allowed to assert, as exceedingly probable, that the dew-points, upon the whole, vary with the declination of the moon, and in the same manner as the tides of the sea do. I have been induced to publish the above remarks from having seen a popular notice of M. ARAGO's paper on lunar influence. One of the first remarks is, that the number of rainy days is increased by the moon's perigee. The number of rainy days in apogee being to those in perigee: 1069 1169. This would agree very well with the notion of : 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 inequalities of pressure alone. Medical men will be able to judge, whether the recurrence of a very high 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 up by our correspondent, but we regret that in calculating some of them he should have selected those columns of the meteorological registers, which were perhaps the 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 depression of the wet bulb thermometer is at a minimum, and least trust-worthy for shewing the hygrometric effects of aërial currents, which are also at that hour generally lulled and quiescent. The aqueous tension calculated from the depressions, 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 4 P m. to point out the lunar influence if perceptible, on the atmosphere : for its indications are alike affected by the direc tion of the aërial 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 meteorological 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. TABLE Shewing the quantity of Rain that has fallen in the first four months of each Total, 0.02 1.65 0.40 0.25 0.04 1.08 0.78 .. 1.96 4.45 4.15 0.34 1.15 2.88 0.55 Shewing the quantity of Rain which fell in each season of the Sept. .. 1.96 4.45 4.15 0.34 1.15 2.88 0.55 * * * 7.04 7.22 6.76 2.30 5.54 8.61 1.08 4.97 7.04 7.22 * * 1.34 3.59|2.81|2.44 0.30 5.67 1.10 4.22 1.91 6.55 5.26 7.33 9.40 6.60 10.20 6.22 6.84 5.95 4.53 5.12 10.27 2.47 2.05 NOTE. The days of maxima are marked with an asterisk, that they may meet the period, but not such as to invalidate the results. No. 1. year for eight years; and the distance of it from the day of New Moon. year in Calcutta, and their distances from the day of New Moon. 2.08 4.03 3.40 9.98 17.87 8.36 6.72 4.81 3.91 1.107.26 $1.39 5.02 1.50 5.34 * 3.38 1.60 2.58 0.59 4.10 5.24 0.98 4.80 2.56 386 2.71 0.50 0.66 4.43 1.46 3.52 7.11 6.83 12.62 5.53 9.47 8.13 6.31 7.51 6.61 12.68 11.07 11.98 9.64 6.43 * in the same period. * * * eye more readily. P. S. some incorrectness has since been discovered in the 4th |