316 Meteorological Summary for 1827. — Hampshire. 



sphere on the mercurial column this year, is T §-^ of an inch lower 

 than that of last year, and -^^ of an inch higher than the mean of 

 the last twelve years. The yearly maximum pressure is not high, 

 nor the minimum comparatively low. 



The aggregate of the spaces described by the alternate rising 

 and falling of the quicksilver, is 14*59 inches greater than in 1826. 



The number of changes in the Barometer this year, viz. 266, co- 

 incides with that of 1826 and 1816, and is only four short of the 

 annual average for the last twelve years. Although the aggregate 

 of the spaces differs very much in different years, yet the yearly 

 number of changes is pretty uniform ; and the average time of each 

 change during the last twelve years, is 32J hours nearly. The 

 annual uniformity of these changes, as influenced by the varying 

 weight of the atmosphere on the column of quicksilver, might have 

 first suggested to meteorologists the idea of the existence of atmo- 

 spherical tides, as chiefly effected by the moon's attractive force on 

 the spheroidal mass of the earth's atmosphere. But these changes 

 not happening regularly, compared with the regularity of the tides 

 of the ocean in connection with the moon's motion, as sometimes 

 they are quick and at other times very slow, at least near the earth's 

 surface, a train of imperceptible effects, besides the moon's sup- 

 posed attraction, should therefore be taken into consideration to 

 account fairly for the atmospherical tides, as the diurnal action of 

 the sun's calorific rays upon the atmosphere ; the ascending heat 

 from the earth in the spring and summer months ; the rarefaction 

 of the atmosphere, particularly under the sun's vertical rays and 

 about the equator ; the consequent perturbations of the air, and 

 dispersion of dry and moist winds, according to their position, to 

 every known place on the earth ; and the influence of the seasons 

 upon the constitution of the atmosphere in every climate without 

 the tropics of Cancer and Capricorn. 



Temperature. — In the temperature of the atmosphere we ge- 

 nerally feel more interest than in the pressure, from the effects it 

 often produces in us when too much exposed to the extremes of 

 either cold or heat. The heat we sustain beyond the temperature 

 of the ground, is the effect of the solar rays on the earth and sur- 

 rounding atmosphere, while the earth moves in that part of its orbit 

 which coincides with the northern signs of the ecliptic ; for while it 

 moves through the space occupied by the southern signs, the mean 

 temperature of the atmosphere in this latitude is almost invariably 

 below the mean temperature of the ground, and especially during 

 the time it moves through Capricornus, Aquarius, and Pisces. How- 

 ever, in respect to the temperature connected with the seasons, it 

 is sometimes reversed for three or four weeks in the spring or au- 

 tumn. A deviation of this sort occurred last February, the mean 

 temperature of that month being 2| degrees below the mean of 

 January. Two other deviations also occurred in 1826, as explained 

 in our Meteorological Summary for Hampshire that year. 



The mean temperature of the external air this year is about a 

 degree below that of last ; but it is nearly three quarters of a de- 

 gree higher than the mean of the preceding twelve years. 



The 



