Box 13, Folder 2: Atmospheric Tides 1866-1869

[1866 see copy - 1864 & 5] [Lunar Tide] [I.A. Lapham]

The following table is made up from my observations, at various times, since the year 1836 and from. all other accessible sources, including the self registering tide gauge of the Lake Survey.

The zero, being the same used by the Milwaukee City authorities will, doubtless be always preserved for future comparison and use. I have ascertained that it is five feet lower than the zero adopted by the U.S. Lake Survey; one four & forty hundredths higher than the one used by the late Lt. Col. J. D. Graham at Chicago; and fifty five* hundredths of a foot higher than the zero adopted by the City Engineer at Chicago.

The highest water known was in July 1838 (4.00 feet above) and the lowest was in March 1848 (1.65 ft below); the range from highest to lowest water being 5.65 feet.

The general mean stage of water for the past thirty one years is 1.20 ft. above the Milwaukee zero. The water is, as a general rule, below the mean of the year for the six months ending April 30th, and above it for the six months ending November 30th.

In August 1849 I made a series of abbreviations which moved clearly the existence of a slight linear tide on Lake Michigan; a fact that was publicly announced at the time; the resulting curve corresponding almost exactly with that yielded afterwards by the self registering tide gauge.

The figures are in feet & decimals - The sign (-) minus shows below the zero.

* by Comparing results of wide Gauge Obs.

Some of the months only one observation some month 6 times daily - 2 mo hourly night & day. -

[unclear which text is correct due to the amount of pencil markings:] A Table showing the mean monthly level of the surface of Lake Michigan at the Port of Milwaukee above the city zero of street grades adopted in the City of Milwaukee, Wisconsin which is the level of the river (& Lake) in March 1836; Prepared by I. A. Lapham

[table by Month from 1836 to 1866]

Lake Michigan Lunar tide about 1 1/4 inches

No. 4

The following table is made up from my observations, at various times, since the year 1836 and from all other accessible sources, including the self registering tide guage of the U. S. Lake Survey

Copy of table made by Dr. I. A. Lapham Milwaukee Wis

In August 1849 Dr. Lapham made a series of observations which proved clearly the existence of a slight lunar tide on Lake Michigan; a fact that was publicly announced at the time; the resulting curve corresponding almost exactly with that yielded afterwards by the self registering tide guage.

Milwaukee zero (or low water of March 1836) is five feet lower than the zero adopted by the U. S. Lake Survey - 1.40 ft higher than the one used by Lt. Col. J. D. Grahame at Chicago and .[?]5 of a foot higher than the zero adopted by the city engineer at Chicago.

[table]

This page is blank

[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.