CLIMATfiS or CJREAT MALVERN AND LONDON. 219 



distantly situated, and noted by different persons j thus they may 

 not be observed at precisely the same period, and this, should they 

 happen to be rising or falling rapidly at the time, would introduce 

 some error ; again, at the time of observation, one person may 

 give a tap with his finger to the tube — the other may not, which 

 will sometimes make a difference of some hundredths, the mercu- 

 ry, often adhering slightly to the glass, resuming its proper indica- 

 tion when gently moved or shaken. 



From these considerations, (to say nothing of the probable error 



in printing three different decimal figures thirty times every 



month) we feel much inclined to conclude that the fluctuations of 



the barometer at London and Malvern are simultaneous^ and very 



nearly (quite ?) equal, and, if so, of course in all places intervening. 



In September, the first month of the autumnal quarter, 



the maximum of the barometer, in London, was 30.4(51, the 



minimum 29.315 ; the mean 30.026, and the range 1.146 



inch. In Malvern the maximum was 29.877, the minimum 



28.740 J the mean 29.425, and the range 1 .137. 



In October, the maximum, in London, was 30.619, the 

 minimum 29.237 5 the mean 29.996, and the range 1.382. 

 In Malvern the maximum was 30.027, the minimum 

 28.734 5 the mean 29.401, and the range 1.293. 



In November, the last month of the autumnal quarter, 

 the maximum of the barometer, in London, was 30.379, the 

 minimum 29.141 j the mean 29.904, and the range 1.238. 

 In Malvern the maximum 29.883, the minimum 28.586 j 

 the mean 29.331, and the range 1.297. 

 For the autumnal quarter — 



Mean Height. Mean Range. 



London 29.975 .,. 1.255 



Malvern 29.385 1.242 



DEW-POINT. 



The atmosphere being everywhere mingled with aqueous vaponr 

 of very variable elasticity, and upon which all those important 

 meteorological phenomena rain, cloud, mist, dew, &c., primarily 

 depend, it is necessary, in any comparison of climates, to estimate 

 the changes it is daily undergoing. The hygrometer enables us to 

 do this — particularly the one now well known as Daniell's Hygro- 

 meter. In the Meteorological Tables published by the Royal 

 Society, there is a column including the dew-point, every morning 

 at 9, A. M. and we are in possession of similar observations at the 

 same hour made at Malvern, and both determined by the above 

 instrument.* 



* It would be almost impossible to describe this delicate instrument so as to be 

 understood without a plate and references ; the result is obtained by gradually 

 lowering the temperature of a dark glass bulb, until a thin ring of dew or moisture 

 is deposited upon it. The precise point at which a thermometer, affected by the 

 process, stands when this appears, is termed the dew-point, or point of condensation, 

 which marks with infallible precision, the comparitive degrees of moisture and 



