290 ABSTRACTS OF THE MAKERSTOUN OBSERVATIONS, 1843. 
TABLE XXVII.—Means of the Maximum Pressures of Wind within 10™ a¢ the Hours of 
Observation for each Month and Quarter of 1843. 
Period. 
January 
February 
March 
April 
May 
June 
July 
August 
September 
October 
November 
December 
Spring 
Summer 
Autumn 
Winter 
The Year 
Diurnal Variation of the Mean Pressures of the Wind.—The means for the month of December are ir- 
regular, presenting three maxima and three minima within the nine observations ; February, March, October, 
and November indicate two maxima and two minima in the twenty-four hours. The maximum pressure occurs, 
in general, about 1" p.m. The following are the periods of the maxima for the mean meteorological and 
astronomical seasons :— 
Seasons. Mean Meteorological. Astronomical. 
Spring, : : OF 50™ p.m. 0» 30™ p.m. Makerstoun mean time. 
Summer, . ; Qh 50™ pM. 2h 90™ p.m. 
Autumn, . . 11 40™.m. 0 40™ p.m. 
Winter, ‘ ; 0» 50™ p.m. 11 50™ a.m. 
The periods for the astronomical group are the most distinct and regular ; from these the maximum pres- 
sure of wind occurs latest in Summer, about an hour after the maximum temperature, and earliest in Winter, 
about an hour before the maximum temperature. In Spring and Autumn the maximum pressures occur about 
an hour before the maximum temperatures. In Autumn of the mean meteorological group a minimum of 
pressure occurs at 7" 10™ a.m. and another at 7 10™ p.m. 
In Spring of the astronomical group minima occur at 7" 10™ a.m. and 7" 10™ p.m. 
In Autumn a minimum occurs at 7" 10™ a.m. 
In Winter a minimum occurs at 5" 10™ p.m., and a maximum at 7" 10™ p.m. 
In the means for the year the maximum pressure occurs at 0 25™ p.m., or an hour before the maximum 
temperature of the air. The pressure increases regularly from 7" 10™ a.m. till 0? 25" p.m., at the rate of 
0-06 Ib., and it diminishes from 0% 25™ till 7" 10™ at the same rate, The forenoon and afternoon branches of 
the mean diurnal curve are therefore straight lines, forming the same angle with the ordinates. 
