It will be noticed that the barometric curve shows the usual double daily maxima and minima, except during the summer season, when, from a cause which I cannot explain, we only have the usual first maximum and second minimum.

The gaseous pressure curve shows a double maximum and minimum during the winter, and has an indication of the same in the spring.

This shows how little dependence can be placed on the readings of the psychrometer when the temperature of the air is much below freezing, even in the hands of a careful observer, and I would, therefore, recommend the discontinuance of the reading of that instrument when the temperature is below freezing. The first minimum of the total pressure varies from 3.30 to 5 a. m.; the second, from 2 to 4 p. m, (excluding the summer minimum as anomalous ;) the first maximum from 9.30 to 10.30 a. m; and the second from 7.30 to 10.30 p. m. Of the gaseous pressure the maximum is from midnight to 3 a. m., and the minimum from 2.30 to 4.30 p. m., the winter curve being incorrect on account of the lowness of the temperature.

In the thermometer curves, the almost perfect parallelism of the curves of the dry and wet bulbs during the winter shows, as before noticed, the want of accuracy in the instrument during cold weather.

The minimum of the dry bulb occurs at 3.30 a. m. during the spring, sumand winter, but in autumn it is at 5 a. m., while the maximum occurs at 2 p. m. in the spring, and at 2 30 p. m. during the rest of the year.

mer,

The minimum of the wet bulb varies from 3 to 4.30 a. m., and the maximum from 2 to 2 30 p. m., being a little in advance of the maximum and minimum of the dry bulb.

I intended to compute from the observations, tables for the hourly connections for the periodic and non-periodic variations of temperature, but have been obliged to postpone it on account of want of time.

The humidity curves have their maxima from 4.30 to 6.30 a. m., or from one to two hours subsequent to the time of minimum temperature, and their minima from 2 to 3.30 p. m. being after the maximum of temperature during the spring and summer, and before during the autumn and winter.

The very depressed winter curve is probably due to the incorrectness of the psychrometer before mentioned.

The curve of downfall of rain and snow generally shows a maximum at about 4 in the morning, and again about 4 in the afternoon, the minimum being about 10 in the morning, and again in the night, thus being opposed to the curve of barometric pressure.

I have never seen this noticed elsewhere, and these records are too limited to establish a general rule of correspondence between the curves, though I think the subject is worthy of further investigation.

The velocity of wind curves shows a maximum shortly after midnight, and a minimum after noon; this is in accordance with the general impression that the wind blows harder during the night than the day, which is commonly true during warm weather, but I did not expect to see it so marked during the storms of winter. During the spring the course of the wind varies quite regularly, considering the shortness of the time of observation, from north 50 west at midnight to north 24° east at 11 a. m.; in the summer from north 47° west at 4 a. m., to north 80° east at 2 p m.; in the autumn from north 870 west at 5 a. m., to north 220 west at 3 p. m.; in the winter from north 710 west at 9 a. m., to north 500 west at 6 p. m.; thus showing that the course of the wind varies during the day opposite to the apparent motion of the sun even during the winter storms, and the differing directions in the several seasons. This subject will be more fully discussed under the head of land and lake breezes.

In the lower lines of tables K, I have given the means of twenty-four hours, and also the means of one hour's tri-daily observation, viz: 7 a. m. and 2 and 38 w-Vol. ii

9

p. m., for the seasons and years. These will be found, together with their differences, in the following tables:

ANEMOGRAPH RECORDS.

Table showing the means of the barometer, &c., for 24 hours, and for 7 a. m. and 2 and 9 p. m.

24 hrs. 7, 2, & 9. 24 hrs. 7, 2, & 9. 24 hrs. 7, 2, & 9 24 hrs. 7, 2, & 9. 24 hrs. 7, 2, & 9.

Thermometer.

Dry bulb..

Wet bulb

Cloudiness

Wind.

Direction....

Force

N. 6° E. N. 6° E. N. 24°WN. 8°WN. 52° W N. 58°WN. 59 W N. 61°WN. 34°WN. 31°W
1.9
2.1

1.9

1.0

0.7

1. 1

0.9

Table showing the differences between the quantities in the above table.

[+ signifies that the 7, 2, and 9 means are greater than those for 24 hours;

It will be seen from the foregoing that the differences of the barometic means at the hours of the tri-daily observations and for the whole day amount to almost nothing, while the temperature varies about a half degree.

The cloudiness is the same, and even the force and direction of the wind correspond very nearly.

Tables L give the hourly records of the direction and relative velocity of the wind at Milwaukee for 1861. These were omitted in the discussion of the winds in the report for 1865, and are added here to complete the records at Milwaukee.

I have not had time to discuss the winds at the several stations for the two years; they are behind, but hope to be able to do so another season.

These records were taken from the sheets of Burnell's Anemograph, kept at Milwaukee by Observer J. A. Lapham.

This instrument is a late invention, and as its mode of working is peculiar, a description of it may not be out of place.

The paper, which is about six inches wide, passes over horizontal rollers moved