CLIMATES OP GREAT MALVERN AND LONDON. 69 



At the same period^ 9 a.^., the minimum of the preceding nighty 

 {by a self- registering minimum thermometer) is noted and put down ; 

 also the temperature of the dew-point, ascertained by Daniell's 

 hygrometer. This does not take more than five minutes. Again, 

 at eleven p. m., or just before going to bed, the observation is repeat- 

 ed; at this time noting the maximum (by a self-registering maxi- 

 mum thermometer) of the preceding day. 



At each observation, the degree at which a thermometer (which 

 should always hang close to the barometer) stands must be recorded 

 and placed just below the barometric height, as shewn above, so 

 that the correction for temj)erature may at any time be made. — 

 JMiscellaneous remarks can be scribbled down at the same time. — 

 In this way, all things necessary for the purposes of any comparison 

 are recorded, and "may be made available at any future period of 

 leisure. At the evening observation, the dew-point is not essential, 

 and we have generally omitted it ; for the ascertaining it, is a little 

 experiment not readily performed by candle-light. 



The Meteorological Table of the Royal Society is now published 

 monthly in the Athenaeum ; and a register kept in the way recom- 

 mended above, would enable any person to institute, with the great- 

 est correctness — by the assistance of Daniell's Meteorological Essays 

 — a comparison on the following daily particulars : Barometer, 

 thermometer, and hygrometer at 9 a. m. ; the height of the former 

 by aid of the temperature placed below the height at which it 

 stands, can be reduced to 32.° The maximum and minimum of 

 the 24 hours can also be compared, together with the state of the 

 wind and weather. 



By devoting an hour of leisure to the purpose, the mean results 

 for each month may be deduced in the usual manner, and all neces- 

 sary correction duly estimated and applied. 



With respect to the instruments which should be employed — 



The Barometers commonly met with are by no means applicable 

 to observations pretending to any accuracy. In the shops of the 

 best manufacturers and opticians no two barometers agree : the 

 height of the mercury is never actually measured in them— they 

 are graduated one from another, and their errors thus unavoidably 

 perpetuated. Few of them have any adjustment for the change of 



