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XII. — On the Constants of the Barometric Formulce wh'c make correct allow- 

 ance for the Hijgrometric State of the Atmosphere. By Henry Laws Rennt, 

 M.B.I.A., Lieutenant, Royal Engineers, Betired List. 



EeadJunel4, 1858. 



IN a paper which I have already submitted to the Royal Irish Academy, and 

 which has been published by the Academy, I have given a formula which 

 makes correct allowance for the hygronietric state of the atmosphere. In this 

 paper I have stated strongly the necessity of a new constant, to be determined 

 by a considerable number of observations, hygrometric as well as barometric, 

 inasmuch as the constant recommended by Laplace (viz., 18336'0 metres 

 = 60158-57 English feet), having been obtained without a systematic and cor- 

 rect consideration of the influence of the vapour of the water of the atmosphere, 

 must of necessity be erroneous. 



In submitting my former paper to the consideration of the Academy, I was 

 aware that such paper, without a new constant, was no n ore than a theory prac- 

 tically useless ; but as I had reason to believe the theory sound, having studied 

 it with very great care, I did not hesitate to submit the formula containing it 

 (though incomplete) to the Academy, being aware that at any future period, 

 any person acquainted with the subject, and having opportunity to make 

 the necessary observations, could with faci i _, work out the desired new 

 constant. 



Circumstances have enabled me to obtain the new constant, as also much 

 valuable information connected with the subject of barometric observations, 

 which I have now the honour, very respectfully, to submit to the judgment of 

 the Academy. 



When, in my former paper, I stated the necessity of obtaining the new 



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