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REPORT ON METEOROLOGY.
BY J. K. MACOMBER, PROFESSOR OF PHYSICS.
Summary of the work on Meteorology at the Iowa State Agricultural College, at Ames, Iowa, from 1876-1883, inclusive. Latitude 42° north, longitude 93° 38' west of Greenwich. Height above the sea, 1,000 feet.
The meteorological work was commenced in 1875, but, as the records for that year are incomplete, it was thought best to give only the records from 1876.
In table number one will be found the mean monthly and mean annual temperature for seven years. The mean of the seven years gives the annual temperature of the place as 48°.12. The lowest was in 1876, 460.4, and the highest in 1878, 490.7.
In table number two will be found the mean temperature of the seasons.
In table number three is to be found the highest and lowest temperatures for the different months. The highest in the seven years was July, 1878, and June, 1882, when the temperature was 98o. The lowest was in January, 1879, when it was 300 below zero.
Table number four shows the time when the earliest frosts were noticed.
Table number six gives the mean monthly and mean annual rainfall. The mean annual rainfall for the seven years is 35,22 inches. All snow is melted and measured as rain. The heaviest rainfall of any year was in 1881, when it was 51.92 inches. The least fell in 1880, 29.5 inches. The greatest in any month was in July, 1881, 16.31 inches, and the largest amount in twenty-four hours was on the night of July 10, 1881, when 5.35 inches fell.
Table number six gives the rainfall for the seasons. The average
for summer is 16.02 inches; autumn, 8.55 inches; spring, 8.02 inches, and winter, 2.42 inches.
Table number seven gives the mean humidity from April to October.
Following the records taken at this place, I have appended a summary of the records from Davenport, Scott county, Iowa; Tabor, Fre mont county, Iowa; Grinnell, Poweshiek county, and a record of the rainfall at Sioux City, for eleven years.
I am under obligations to Dr. J. F. Sanborn for the report from Tabor. The records from Davenport were sent me by Messrs. W. H. Pratt and B. F. Tillingbast, and were taken by the United States Signal Service observer, Lieutenant Robert Martin. The observations from Grinnell were taken by Messrs. W. H. Brainerd and E. G. Worden, students in Iowa College. The Hon. George H. Wright, of Sioux City, has furnished me with the records from that place. I wish to express my obligations to all these gentlemen for the favors at their hands.
TORNADUES AND CYCLONES.
An account of the meteorology of Story county for the past eight years would be very incomplete without a brief notice of the tornadoes which have swept over it.
On April 8, 1882, at six o'clock and fourteen minutes, by Chicago time, a small tornado passed through the grounds of the College. Its direction was due north, and it was traced from a point about ten miles south of here over a path about twelve miles long. It entirely destroyed the house of Mr. Keltner, about two miles south of the College. Mr. W. McCarthy's house, three fourths of a mile south of the College, was also completely destroyed and the occupants somewhat injured. On the College farm a large amount of damage was done. A portion of the brick wall of South Hall was bulged outward by the pressure of the wind inside the house caused by a door blowing open. The south tower of the main building was seriously damaged. North Hall had both gable ends blown in above the first floor, and all the roof carried away except a small portion in the center. Many trees and smaller buildings about the campus were damaged. No people were killed, although for a time it was thought that several were seriously injured.
This was a genuine tornado or whirlwind, the direction of rotation being from right to left, or opposite that of the hands of a watch.
Its velocity in a direction from south to north was twenty-four miles per hour. Calculations made from various data show that the velocity of the wind in its rotary motion was from one hundred to one hundred and fifty miles per hour.
THE TORNADO OF APRIL 17, 1882, COMMONLY KNOWN AS THE
NELL TORNADO." On June 17, 1882, a terrible tornado swept over the western portion of Boone county, through Story county, and thence in a southeasterly direction to Mt. Pleasant in this State. It was first seen in this county about four miles south of the College, and had the appearance of a long, slender column reaching from the clouds to the earth. The column was nearly a mile long, and perhaps four hundred feet in diameter. In passing through this township it broke into two distinct tonadoes, which moved nearly parallel about two miles apart, and then united after crossing the Skunk river. Probably ten thousand dollars would not pay the damage done in this county alone.
I shall only give a brief summary of the important peculiarities and facts of this tornado.
First-Its general direction was from northwest to southeast.
Second-The wind rotated from right to left, or, in the opposite direction of the hands of a watch.
Third—The cloud moved over the State at the rate of about fortysix miles per hour.
. Fourth--The velocity of the wind in the tornado was from two hundred to three hundred and fifty miles per hour.
Fifth-At times the tornado resembled a funnel with the little end down; then a long serpent, and then at other times it resembled two cones with their bases on the ground and in the clouds meeting in mid-air.
Sixth--The width of the tornado varied at different times from two hundred to one thousand feet.
Seventh-It frequently rose from the ground and drew into the clouds, and after passing some distance the funnel would let down again and commence its work of destruction.
Eighth-This tornado swept through the town of Grinnell in Powe. shiek county, and killed and injured a large number of people. It is probable that not less than half a million dollars worth of damage was done in its course through Iowa.
TABLE NO. I. Table showing the mean annual temperatures, and also the mean monthly temperatures, from 1876–1883. Annual mean temperature for seven years, 48.12o.
1876. 1877. 1878. 1879. 1880. 1881. 1882. 1883.
13.61 21.3 36.6 50.1 63.1 70.2 78.3 72.3 59.6 60.2 33.6 16.4
*The observations for 1883 not completed at the time of publication.
Table showing the mean temperature of the seasons from 1876– 1873.
In getting the mean temperatures of each winter the mean temperature of December of the previous year is included.
1876. 1877. 1878. 1879. 1880. 1881. 1882. 1883. Means
14.61 45.9 76. 50.5
28.6 46.4 71.5 51.5
11.7 45.2 71.3 *
73.6 71.3 73.5 Autumn.
49.2 *Not completed at time of publication.
Table showing the maximum and minimum temperatures observed for the years 1876-1883. Observations taken at 7 A. M. and i P. M.
TABLE No. III.
FEB. MAR. APR. MAY. JUNE. JULY. AUG. SEPT.
47 -12 59 -10 481-10161 1877.
56 1961 570 -676
56 --659 770 23 78
43 --30 441--1476 183
57 368 -461 0 81
35 --25 40 -16 12 176
43 --955 --659 947
36 -21 39 -2355 2 86 The sign minus (--) means below zero.
39 931 54 93 46 85 35 76 14163 -754-24
59 83 53 90 38 79 31 62 13 51 --19