Atmospheric Tides, January 1869

[Atmospheric Tide]
[Jan: 1869]

To ascertain whether the hourly oscillations of the Barometer, indicating a tidal wave in the atmosphere could be determined, as suggested by Col R.S. Williamson, by a single days observation, I made such observations at Milwaukee commencing at 7 am Oct 19 1868. The moon reached the meridian 3 hours after the sun-had 18* south declination-the sun's declination 10* south. The abnormal oscillation was manifested by a pretty uniform rise of the Barometer during nearly the whole day. The temperature did not vary much during the 24 hours, being at 7 am 41* at 2 pm 45* at its maximum 49* at 9 pm 43* and at its minimum depression during the night 41* But little of the atmosphere tide an therefore be attributed to change of temperature between the day and night. The sky continued to be uniformly cloudy, wind moderate, the air contained from 61 to 77 m ct of the amount of aquors vapor it was capable of holding; the messine of vapor being equivalent to from 0.181 to 0.198 inches of mercury. So the wave could not have been much affected by changes in the hypometrical condition of the atmosphere.

Hence there observations were favorable for showing the effect of astronomical causes upon the atmosphere.