Heat. 



463 



1 That liquids, separated by porous plates, reciprocally 

 penetrate in part through these plates. This, however, 

 has been previously stated. 



2. The proportion of the volume, which passes from 

 both solutions in equal time, depends on the nature of the 

 solutions and partition as well as the temperature. It is 

 not, however, a necessary condition, that a greater volume 

 should pass through the plate from the one solution than 

 from the other ; or, that on one side of these plates a 

 greater volume should enter, as Dutrochet erroneously 



thinks. 



3. When the diffusion is terminated, the volume re- 

 maining on each side of the partition may be calculated 

 from the original volume, being inversely, as the square- 

 root of its density ; as Graham has shewn with regard to 

 gases. If equal volumes of a saturated solution of com- 

 mon salt, and solution of sugar of the specific gravity 1-078, 

 are separated by a bladder, the first increases in volume at 

 first, but diminishes in specific gravity, in a greater degree 

 than would take place by a regular mixture. 



4. The height to which solutions ascend in capillary 

 tubes, is often proportionate to the quantity of liquid dif- 

 fused'. Thus, some solutions, which rise highest in capil- 

 lary tubes, are conveyed in strongest streams, but there 

 are many exceptions to this rule. 



5. Liquids are not only conveyed through solid porous 

 plates, but also through a short canal between mercury 



and glass. 



6. By the chemical action of electricity, the proportion 

 of the liquid which passes may be increased ; but this cause 

 only operates, in so far as it separates acids, alkalies, and 

 salts. 



ARTICLE X. 



ANALYSES OF BOOKS. 



On the Application of the Hot Blast in the Manufacture of 



Cast Iron. By Thomas Clark, M.D., &c. (Trans. Royal 



Soc. Edinb. xiii.) 



The substitution of hot for cold air, in the blast furnaces of the iron 



manufactory, is an improvement which suggested itself to the inge- 



