78 



VI. 



TABLE OF THE ELASTIC FORCE OF AQUEOUS VAPOR, 



EXPRESSED IN ENGLISH INCHES OF MERCURY FOR TEMPERATURES OF FAHRENHEIT, 

 REDUCED FROM REGNAULT's TABLE. 



THE values of the elastic force of vapor furnished by V. Regnault, which are 

 found in Table 1. of this Hygrometrical set, are derived from a series of experiments 

 conducted, during several years, with great care, consummate skill, and all the means 

 of precision which are at the disposal of modern science. The methods of investi- 

 gation, and all the steps in each experiment, were minutely described and submitted 

 to the judgment of the scientific, successively in separate papers in several volumes 

 of the Annales de Cliimie et de Physique, and collectively in his final Report to the 

 Minister of Public Works, (see above, p. 9,) which fills Volume XXI. of the Me- 

 moires de PInstitut de France. The confidence which has been deservedly granted 

 to these determinations by nearly all scientific men, is increased by the fact that one 

 of the best physicists and experimenters in Germany, Professor Magnus, came, 

 about the same time, to results so little different, that both tables, for most purposes, 

 may be considered identical. (Compare below, Table XXII.) It seems, therefore, 

 that these values ought to be used in our hygrometrical tables, as has been done 

 in France, in preference to the older and less reliable determinations on which they 

 are based. 



Though Regnault's table of the elastic force of vapor is considered, even, it is be- 

 lieved, by a majority of scientific men in England, as the most reliable which science 

 now possesses, the author is not aware that any extensive reduction of it to English 

 measures, such as is wanted for meteorological purposes, has been as yet published ; 

 still less a series of tables based on these values. Such a set of hygrometrical tables 

 in English measures, corresponding to the preceding one in French measures, is 

 offered here, which, it is hoped, supplies a real want felt by a large number of me- 

 teorologists. 



Table VI. is Regnault's Table of the Elastic Force of Vapor as given in Table I., 

 reduced to English measures, in which the fourth decimal is given in order to secure 

 the third, and otherwise to facilitate the computations. From these values Tables 

 VII. to X. have been computed. 



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