STUDIES ON FERMEXTATIOX. 287 



gas, except when the flask was slightly shaken, in which case 

 rather large bubbles adhering to the deposit rose, carrying with 

 them some solid particles, which quickly fell back again, whilst 

 the bubbles diminished in size as they rose, from being partially 

 taken into solution, in consequence of the liquid not being 

 saturated. The smallest bubbles had even time to dissolve com- 

 pletely before they could reach the surface of the liquid. lu 

 course of time the liquid was saturated, and the tartrate was 

 gradually displaced by mammillated crusts, or clear, trans- 

 parent crystals of carbonate of lime at the bottom and on the 

 sides of the vessel. 



The impregnation took place on February 10th, and on March 

 15th the liquid was nearly saturated. The bubbles then began 

 to lodge in the bent part of the exit-tube, at the top of the 

 flask. A glass measuring-tube containing mercury was now 

 placed with its open end over the point of the exit-tube under 

 the mercury in the trough, so that no bubble might escape. A 

 steady evolution of gas went on from the 17th to the 18th, 

 17*4 c.c. (1"06 cubic inches) having been collected. This was 

 proved to be nearly absolutely pure carbonic acid, as indeed 

 might have been suspected from the fact that the evolution did 

 not begin before a distinct saturation of the liquid was observed.* 



The liquid, which was turbid on the day after its impregna- 

 tion, had, in spite of the liberation of gas, again become so 

 transparent that we could read our handwriting through the 

 body of the flask. Notwithstanding this, there was still a very 

 active operation going on in the deposit, but it was confined to 

 that spot. Indeed, the swarming vibrios were bound to remain 

 there, the tartrate of lime being still more insoluble in water 

 saturated with carbonate of lime than it is in pure water. A 

 supply of carbonaceous food, at all events, was absolutely 

 wanting in the bulk of the liquid. Every day we continued to 

 collect and analyze the total amount of gas disengaged. To 

 the very last, it was composed of pure carbonic acid gas. Only 



* [Carboinc acid being considerably more soluble than other gases 

 possible under the circumstances. — Ed.] 



