and the Hygrometer of J, Berzelius. 1 19 



sembling the original one, and preserved for use, and which 

 were found upon trial to give correspondent results in diffe- 

 rent parts of the scale. Dr. Franklin recommends slips of 

 mahogany for hygrometrical purposes : my experiments, 

 however, were made with rods of old dry deal, answering 

 the preceding description. The preference was given to this 

 kind of wood, because temperature has but little effect on 

 its dimensions ; besides which, I did not recollect at the 

 time the recommendation given to mahogany by the cele- 

 brated philosopher of America. 



Perhaps, sir, 1 should never have troubled you or any other 

 journalist with the preceding trifle, had it not been for a 

 paper which appears at the 39th page of your present vo- 

 lume. This is a description of a hygrometer recommended 

 to the public, by the inventor J. Berzelius, on the suppo- 

 sition that Mr. Dalton's theory of mixed gases is consistent 

 with the phenomena of meteorology. Tn attempting to 

 vindicate the merits of his instrument, this foreigner asserts, 

 that Dalton has proved the water of the atmosphere to be 

 independent of the air. To this we may reply, It is a fact 

 established by different philosophers of the last century, that 

 water assumes the form of a gas under an exhausted receiver 

 at any temperature greater than 32°. It has also been shown 

 by M. De Luc, that the presence of air retards the produc- 

 tion of the aqueous gas ; but I will venture to say that M. 

 Berzelius goes too far when he asserts that Mr. Dalton has 

 proved the water of the atmosphere to be independent of the 

 air. The perfect freedom of atmospherical vapour is un- 

 questionably a favourite opinion with this gentleman ; but 

 in what part of his works, or in what manner, is the propo- 

 sition demonstrated ? An explicit answer to this question" 

 is absolutely necessary ; because M. Berzelius has adopted 

 principles in the construction of his hygrometer, which 

 must remain precarious until the subject in debate has been 

 decided in favour of the new hypothesis. M. Berzelius's re- 

 marks on Mr. Daltoo's table, ex In biting the expansive force 

 of vapour, have nothing to do with the business of hygro- 

 metry, so long as the preceding uncertainty can be objected 

 to the opiuions of the latter gentleman. This table may be 



M2 true 



