BY COMPRE&SIOWc 



Explanation, 



Sll 



Column I. contains the number affixed to each of the specr- Explanation o^ 

 mens, whose properties are expressed in the table. the table of 



rri {• . ^ , . , , specific %v2.\t~ 



1 he tirst eleven are the same with those used in the paper ties, &i. 



read in this Society on the 30th of August 1804, and published 

 in Nicholson's Journal for October following,, and which refer 

 to the same specimens. No. 12. Is a specimen of yellow mar- 

 ble, bearing a strong resemblance to No. 3. No. 13. A speci- 

 men of chalk. No. 14. Shews the average of three trials witk 

 chalk. No. 15. Some pounded chalk, rammed in the manner 

 followed in these experiments. In order to ascertain its specific 

 gravity, I rammed the powder into a glass-tube, previously 

 weighed ; then, after weighing the whole, I removed the chalk, 

 and filled the same tube 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 VIIL 



Column II. Weight of the substance, dry in air, after expo- 

 sure, during several hours to a heat of 212° of Fahrenheit. 



Column III. Its weight in water, after lying long in th« ■ 

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

 being carefully removed. 



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

 ure being removed by the touch of a dry cloth ; but no tim« 

 being allowed for evaporation. 



Column V. Difference between columns II. and III, 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 

 <]ry substance. 



Column VIIT. Sum of columns V. and VI., or the real 

 weight of water displaced by the body. 



Column IX. Specific gravity, by the common mode, result- 

 ing 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 ex- 

 pressed in column X. correspond very well to the idea which 

 is formed of their comparative deasities, from other circum- 



stances* 



