212 Effects of Heat modified by Compression. 



with water. I thus ascertained, in a direct manner, the 

 weight of the substance, as stated in Column II., and that 

 of an equal bulk of water, stated in Column VIII. 



Column IT. Weight of the substance, dry in air, after 

 exposure, during several hours, to a heat of 212° of Fahren- 

 heit. 



Column III. Its weight in water, after lying long in the 

 liquid, so as to perform its full absorption; and all air-bub- 

 bles being carefully removed. 



Column IV. Weight in air, wet. The loose external 

 moisture being removed by the touch of a dry cloth, but no 

 time being allowed for evaporation. 



Column V. Difference between Columns II. and IIT., or 

 apparent weight of water displaced. 



Column VI. Difference between Columns II. and IV., or 

 the absorption. 



Column VII. Absorption reduced to a per centage of the 

 dry substance. 



Column VIII. Sum of Columns V. and VI., or the real 

 weight of water displaced by the body. 



Column IX. Specific gravity, bv the common mode, re- 

 sulting from the division of Column II. by Column V. 



Column X. Specific gravity, in the new mode, resulting 

 from the division of Column II. by Column VIII. 



The specific gravities- ascertained by the new mode, and 

 expressed in Column X. correspond very well to the idea 

 which is formed of their comparative densities, from other 

 circumstances, their hardness, compact appearance, sus- 

 ceptibility of polish, and weight in the hand. 



The case is widely different when we attend to the results 

 of the common method contained in Column IX. Here the 

 specific gravity of chalk is rated at 2*40S, which exceeds 

 considerably that of a majority of the results tried. Thus, 

 it would appear^ by this method, that chalk has become 

 lighter by the experiment, in defiance of our senses, which 

 evince an increase of density. 



This singular result arises, T conceive, from this ; that, 

 in our specimens, the faculty of absorption has been much 

 more decreased than the porosity. Thus, if a piece of crude 



chalk, 



