Meteoro/ogy. 



209 



used. In this way Professor Meinicke obtained from a two 

 feet plate machine a constant light in his apartment equal to 

 that of the moon, and even surpassing it ; and by enclosing his 

 system of sparks in tubes filled with rarefied hydrogen gas, in 

 which gas it is assumed that the electric spark is more than 

 doubled in brilliancy, thinks it will be easy to enlarge the plan 

 to any extent. 



11. Meteorology. 

 [The very beautiful tables, accompanying this communication, we hare 



been obliged to omit, in consequence of the space which tliey would 



occupy.] 



Sir— You will herewith receive a Meteorological Map of the 

 year 1819, containing the altitude of tlie barometer every day 

 at noon, accompanied with a register of the thermometer, and 

 wind at the same time ; in addition to the map I have sub- 

 joined the following remarks on the whole year, which, should 

 you consider worthy of a place in the Journals of the Royal 

 Institution, are much at your service. 



I am, Sir, respectfully yours, ^c, 



John Lewthwaite. 



Rotherhithe, February 12, 1820. 



IblO. 



Months. 



January . . 

 February 

 March . . . . 

 April . . . . 

 May . . . . 

 June . . . . 

 July . . . . 

 August . . 

 September 

 October . . 

 November 

 December 



Slean of the Baro- 

 meter at Noon. 



29,911 

 29,794 

 30,027 

 29,932 

 30,024 

 30,048 

 30,122 

 30,150 

 30,118 

 29,973 

 29,889 

 29,877 



Mean of the year 29,9887^ 



Mean of tlie 



Tlierniomettr 



at Noon. 



45° 



45 



49 



56 



64 



66 



72 



74 



66 



57 



46 



41 



561- 



Voi.. IX. 



