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IX. On the Lunar Atmospheric Tide at Singapore. 
By Captain C. M. Elliot, Madras Engineers, F.R.S. 
Received December 18, 1851, — Read March 11, 1852. 
At the commencement of the year 1847, a paper by Colonel Sabine, R.A., V.P.R.S., 
was read before the Royal Society on the Lunar Atmospheric Tide at St. Helena. 
The influence of the moon upon the barometer, although small in amount, was 
shown in a very striking and decided manner; for after eliminating the regular 
diurnal variation, the differences arranged in lunar tables showed a decided maxi- 
mum, both at the superior and inferior culmination of the moon, and a decided 
minimum at its rising and setting. 
The effect which the moon’s position, relatively to the meridian of the place, had 
upon the barometric pressure, was publicly noticed, about the middle of 1842, by 
Captain Lefroy, R.A., who appears to have had his attention directed to it from the 
first establishment of the observatory at St. Helena. 
On the receipt of Colonel Sabine’s paper, 1 was anxious to ascertain if the fact of 
the moon’s influence, so clearly and decidedly shown at St. Helena, could be similarly 
proved by the Singapore barometric observations. 
I therefore determined, before leaving England for India, to proceed upon the 
plan adopted by Colonel Sabine, and in order that a comparison might be made be- 
tween the results at Singapore and at St. Helena, have copied to a considerable 
extent the form of the different lunar tables drawn up by him in his very valuable 
paper. 
The observatory at Singapore was in latitude 1° 18' 32" north, and longitude 103° 
56' 30" east of Greenwich. The cistern of the barometer was a few feet above high- 
water mark: the barometer was made by Newman: the diameter of the tube 
= 0’532 inch. The observations of the barometer, by my assistants, were made at 
every two hours during the whole of 1841, the early part of 1842, and that of 1843 ; 
during the rest of the time, to the close of 1845, at every hour. 
In making out the Tables, showing the moon’s effect upon the barometer, I have 
only taken complete astronomical days, from noon to noon ; and as Sundays were 
omitted, and as the observations commenced at midnight on Sunday and terminated 
at 1 1 p.M. on Saturday, the broken portions of Monday and of Saturday have not 
been taken into consideration ; the mean, however, of the entire month has been 
assumed to be identical with the mean of these complete days. 
The Barometer Tables, corrected to 32°, having been made out, the mean monthly 
