Meteorological Summary f(n- 1822. — London. 157 



August : this coincides nearly with the proportion of meteors 

 which that month bears to the annual number that have been 

 seen here for some years past. 



Now, as the maximum temperature of the ground takes place 

 generally at the close of August, or the beginning of Septem- 

 ber, which is some time after the greatest summer heat of the 

 sun's rays, it naturally induces a belief that the exhalations 

 from the earth, (whose com.position must be of various gaseous 

 qualities,) uniting with the gases of the atmosphere, may be 

 the chief agent in their production, particularly, as these sum- 

 mer meteors are much nearer the ground than those seen m 

 the winter evenings. The evaporation is more than double 

 that of last year; which is but a natural result, considering the 

 dryness of the spring and summer months, aiid the uncommonly 

 high mean temperature of the air. 



Rain has fallen more or less on 181 days, of which 64; whole 

 days and nights is the real time it has rained. July, October, 

 and November, afforded more than one-half of the amount of 

 this year's rain ; and June, July, August, and September, more 

 than one-half the amoimt of the evaporation. 



To the Editors of the Philosophical Magazine and Journal. 



Coinciding in opinion with my worthy friend, and your able 

 and scientific correspondent, Mr. Thomas Squire of"^ Epping, 

 that the best practical results would ensue from a comparison 

 of meteorological observations throughout the country, I have 

 forwarded you the mean atmospheric pressure, in its effect upon 

 a column of mercury, taken at 10 o'clock daily in the City; 

 also the maximum and minimum of the same for each month 

 of the past year; the elevation of the place, taken at the mean 

 of several observations, at 60 feet above the level of the sea : 

 assuming as data the correctness of the given elevation of the 

 apartments of the Royal Society, Somerset- House, the latitude 

 of the place of observation 51° 30' 38", the longitude 21 "-2 

 (in time) west of Greenwich ; the radius of tlie earth assumed 

 as S954.-590 miles. I have stated the elevation particularly ; 

 which should always be given where known, as the force of 

 gravity increases inversely as the square of the chstance from 

 the earth's centre. I am, gentlemen, 



Your obedient servant, 



Cornhill, 15th Feb. 1823. 1^, Webster. 



1822. 



