Miscellanies. 20 1 



ADDITIONAL EXTRACTS, BY PKUF. GUISCOM. 



1. Force* of vapor at different temperatures. — The committee ap- 

 pointed some time ago, by the French Institute, to determine the 

 elastic force of the vapor of water, at high temperatures, consisted 

 of Baron de Phony, Arago, Gerard and Dulong. The solu- 

 tion of this important question appears to have been assigned to Ara- 

 go and Dulong, and the result is contained in a report made by Du- 

 long to the Institute, on the 30th of November, 1829. The series 

 of experiments which were prosecuted by them, in order to settle the 

 question upon the most elaborate and solid foundation, was evidently 

 such as does credit to the talents and ingenuity of these distinguish- 

 ed savans. The report at large is contained in the Annates de 

 Chimie et de Physique, Tome XLII1, p. 74, with figures descrip- 

 tive of the apparatus employed. It concludes as follows. 



"The Academy may perceive the result of our experiments is, 

 1st, a verification of the law of Mariotte, as far as 27 atmospheres; 

 2d, a table of temperatures, corresponding to the tension of vapor, 

 which does not exceed 24 atmospheres. 



These researches, always troublesome and often dangerous, might 

 have demanded many years of assiduous labor. Interruptions, which 

 other duties and circumstances beyond our control have occasioned, 

 have long protracted their conclusion. This delay cannot in justice 

 be ascribed to our negligence. Only persons accustomed to physic- 

 al experiments upon a large scale, can appreciate the magnitude of 

 the task imposed upon us, with which there is nothing to our archives 

 to be compared, and which has occasioned on our part a devoted- 

 ness, which die Academy would not probably deem it right to exact 

 from any of its members. We shall not however, regret the time 

 we have bestowed upon it, if the Academy is of opinion that we 

 have worthily fulfilled the commission entrusted to us, and if respond- 

 ent to the wishes of die government, the results that we present, shall 

 be considered by philosophers as an acquisition useful to science." 



The following table exhibits the height of a column of mercury 



O I 



supported by steam, equal to the pressure of 1 to 24 atmospheres, 

 as determined by experiment, and of 24 to 50 atmospheres, by cal- 

 culation. See the table, page 182. 



* A shorter notice on this subject, was printed at p. 181 of the present No. and 

 this notice has been received since* 



Vol. XIX.— No. 1. 26 



