146 Analyses of Books. [Feb. 



there is great reason to believe that it may be successfully- 

 employed for the preservation of animal and vegetable substances 

 for the purposes of food." 



An appendix to this paper gives the following statement : — 



** In investigating the laws of the elastic forces exerted by 

 vapours or gases raised from liquids by increase of temperature 

 under compression, one of the most important circumstances to 

 be considered is the rate of the expansion, or what is equiva- 

 lent, of the elastic force, in atmospheres in different states of 

 density. 



" It has been shown by the experiments of MM. Dalton and 

 Gay-Lussac, that elastic fluids of very different specific gravities 

 expand equally by equal increments of -temperature, or, as it 

 may be more correctly expressed, according to the elucidations 

 of MM. Dulong and Petit, that mercury and air, or gases, are 

 equivalent in their expansions for any number of degrees in the 

 thermometrical scale between the freezing and boiling points of 

 water ; and the early researches of M. Amontons seemed to show 

 that the increase of the spring or elastic force of air by increase 

 of temperature, was in the direct ratio of its density. I am not 

 however acquainted with any direct researches upon the changes 

 of volume produced in gases in very different states of conden- 

 sation and rarefaction by changes of temperature, and the 

 importance of the inquiry, in relation to the subject of my last 

 communication to the Society, induced me to undertake the 

 following experiments. 



" Dry atmospherical air was included in a tube by mercury, 

 and its temperature raised from 32° Fahr. to 212°, and its expan- 

 sion accurately marked. The same volumes of air, but of double 

 and of more than triple the density under a pressure of 30 and 

 65 inches of mercury, were treated in the same manner, and in 

 the same tubes ; and when the necessary corrections were made 

 for the difference of pressure of the removed column of mercury, 

 it was found that the expansions were exactly the same. 



" An apparatus was constructed, in which the expansions of 

 rare air confined by columns of mercury were examined and 

 compared with the expansions of equal volumes of air under 

 common pressure ; when it appeared, that for an equal number 

 of degrees of Fahrenheit's scale, and between 32° and 212° they 

 were precisely equal, whether the air was ^, i, or -^ of its natural 

 density. 



" Similar experiments were made, but they were necessarily 

 less precise, with air condensed six and expanded fifteen times, 

 with similar results." 



XIX. On the Temperature at considerable Depths of the Carib- 

 bean Sea. By Capt. Edward Sabine, FRS. : in a Letter 

 addressed to Sir H. Davy.— (See Annals, N. S. v. 462.) 



XX. Letter from Capt. Basil Hall, RN. to Capt. Kater, com- 

 municating the Details of Experiments made by him and Mr. 



