Daniell on a new Hj/grotneier, 133 



and night, are respectively a« 41 — 52 — 8, and the weight of 

 vapour in the space of a cubic foot is less at night, by 0.07 gr. 

 than in the afternoon*. 



For the sake of comparison, I have selected five periods, 

 during which 1 have been enabled to try experiments con- 

 temporaneous with those in London, at a distance of twenty 

 miles in the country. It would be tedious to give the com- 

 parison at length, I shall therefore only state the mean rcr 

 suits. 



The constant difference of the barometer between the twp 

 places was 0.09 lower in the country. 



Temper. 



Mar. 31st, to April 6th, 7 days, — London, 52^ , 



Country, 53 . 



May 21st, to 31st, 11 days, — London, 58 , 



Country, 69 , 



June 12th,.to Jyne 194;h, 8 days,— rLondon, 58|^ , 



Country, 52 , 



Aug. 5th, to Aug. 7th, 3 days, — ^London, 63^ , 



Country, 60^ , 



Aug. 26th, to Aug. 28th, 3 days, — London, 57^ , 



Country, 56^ , 



It will be seen from this table that the mean quantities of va- 

 pour at these two stations, during these periods, corresponded 

 within a fraction of a degree, too small to name. 



• The editors of the Bibliothique Universelle object to me, that I appear to 

 have been guided by no consideration in the selection of the periods of the 

 day for the performance of my experijnents. But obliged as I have been 

 to snatch a few moments from other avocations, it was necessary to consider 

 at what times I should be least likely to meet with interruption so as to be 

 able to continue the series in a regular manner. If I have not chosen quite 

 the most proper periods, (and that I have not I am most willing to allow,) 

 ths want of academic leisure must plead my excuse ; and I only trust that 

 those who are fortunate enough to have it in their power to devote their 

 whole time to the pursuits of science, and who have more ability for the 

 task, will copoplete the plan wliich I have only been enabled to trace. 



