The barograph curve for the 18th showed an elevation of 0.05 inch, which lasted from 2.50 to 3.20 A.M.

The great fall which occurred from 29-752 ins. on the 19th, was divided into two periods, the first from midnight of the 20th, to the succeeding midnight, and the second from 10 P.M. on 23rd to 6.20 A.M. of the 24th, at which time a sudden depression of 0.055 ins. which lasted ten minutes, was recorded, the barometer afterwards remained stationary until 2.20 P.M. The mean for the 24th was 28.778 ins., the lowest in the month. Rising readings followed to 26th noon, succeeded by falling readings to 4.10 P.M. on the 28th. With the exception of a short interval on the 29th, the rise was uniform to the end of the month, the 31st mean being 29.879 ins. The mean height for the month was 29-525 ins.

TEMPERATURE OF THE AIR. The daily mean temperature increased from 43.3° on the 1st to 54-3° on the 5th, on which day a sudden rise of the thermometer of 5° was registered at 1.50 P.M.

On the 7th there was a sudden fall of 7° at 1.15 A.M. The mean temperature on the 11th was 51.4°, and on the 12th 38.9°. There was a continuous increase in the temperature from midnight of the 12th to midnight of the 13th, and a still farther rise brought the mean for the 15th to 52:3°. The curve for the night of the 19th showed numerous rapid fluctuatious of the thermometer, whilst that of the 21st records an absence of variation from 1 P.M. to midnight. A quick rise between 6 and 9 P.M. of the 26th brought the mean for the 27th to 53.6°. The means for the succeeding days diminished, that for the 30th being 35.8°.

Sudden falls of temperature of 4° were registered at 11 A.M. and 10.40 P.M. of the 27th, and a depression of 2° between 1.0 and 1.50 P.M. of the 29th.

The highest maximum temperature recorded during the month were 57.5° on the 5th, and 58·1° on the 6th, the lowest 43.3° on the 12th, and 40.0° on the 30th.

The highest minimum temperatures were 51.5° on the 5th, and 49.7° on the 6th, the lowest 31.8° on the 20th, and 32.5° on the 12th.

The greatest daily range was 19.9° on the 13th, and the least 1.8° on the 9th. The mean for the month being 9·0°.

The mean daily temperature for December was 46.5°. RELATIVE HUMIDITY.-Very little variation was observed in the amount of moisture in the air, the extremes being 0.97 on the 2nd, 21st, and 30th, and 0.80 on the 12th, 26th, and 31st. The mean being 0.87 (complete saturation=1·00).

VOL. III.NO. I.

E

RAINFALL. The amount of rain measured during December was unusually large, the daily quantities being as follows:

The total fall for the month=5.196 inches.

WIND. The general direction of the wind was:

East-9th, 12th, and 13th.

South-1st, 2nd, and 14th.

South-West-3rd, 4th, 5th, 7th, 10th, 11th, 15th, 16th, 17th, 18th, 21st, 22nd, 27th, and 30th.

West-6th, 8th, 19th, 20th, 23rd, 24th, 25th, 26th, 28th, 29th, and 31st.

The velocity increased during the morning of the 4th from 10 to 30 miles per hour, maintaining the latter rate until noon of the 5th. It then diminished to 8 miles; but at 1.40 P.M. returned to 35 miles. A similar reduction in velocity was registered the next day from noon to 2.30 P.M.

Between 1 and 4 A.M. on the 8th the direction changed gradually from S.E. to W., and on the same day, between 9 and 11 P.M., from W. to N.E. On the 9th the direction veered from W. to N. at 9.20 P.M. 665 miles of wind passed over the instrument on the 14th. There was a change in direction from W. to S. at 11.25 A.M. of the 20th.

During the 27th the velocity was frequently from 35 to 40 miles per hour; but the maximum velocity of 50 miles was registered at 3 P.M. on the 28th, at the same time as the direction changed from S.W. to N.W.

On the 29th and 30th there were several movements of direction between S. and W.

Highest Temperature recorded during the Year...... 90.2° on July 22nd.

NUMBER OF DAYS IN WHICH THE WIND BLEW IN THE FOLLOWING DIRECTIONS:

THE VELOCITY OF INSECTS' WINGS DURING FLIGHT.

BY E. J. MAREY.

(Translated from "Comptes Rendus.")

IT has seemed to me possible to submit to a strict experiment the study of those motions which the eye cannot follow, and the form of which, we cannot discern under normal conditions, on account of their extreme rapidity.

These are the questions which I have tried to solve :—

A. What is the frequency of the movements of the wings? B. What are the different positions which the wing takes in the different phases of each of its revolutions?

C. By what mechanism does the wing, taking the air for its fulcrum, produce the locomotion of the insects?

A. Frequency of the beating of the wing:

Physiologists have attempted to determine the frequency of the movements of the wing, from the sound produced by the insect during flight. They have been compelled to admit very high figures; six hundred vibrations a second, for the common fly (Lacordaire); yet that number must be tripled in cases of very rapid flight. Other insects must produce a far greater number of beats. Naturalists, nevertheless, have been little agreed upon the cause which produces the sound we hear during the flight of insects. Some authors think the sound independent of the wing movements, produced by a special humming apparatus (Chabrier); it is due, according to others, to the alternate movements of the air, in escaping and entering the tracheal tubes.

In face of these discordances, I have sought for a mode of exhibiting, in an unmistakeable manner, each of the beats of the wing of an insect, and the graphic method answers very well for determining their frequency.

I grasped, with a fine pair of nippers, the hind part of the abdomen of an insect, and when it sought to fly, I directed one of its wings in such a way, that it rubbed by its point against the surface of a smoked cylinder, which revolved with a known velocity. The wing, at each of these revolutions, carried away a little of the black of the smoke which covered the cylinder, and left a trace of its passage. This experiment gives a diagram exhibiting the varied forms that are periodically reproduced with the same characteristics, and, consequently, correspond to one revolution of the wing. By