Dixon — The Cohesion Theory of the Ascent of Sap. 



59* 



manner to the preceding. The same capillary carried the index. 

 The surface of plaster exposed to the water was 19*62 sq. cm. 



In this experiment, the volume occupied by the plaster of Paris 

 was 62*1 c.c. The distance moved through by the index (allowing 

 for temperature was 550 mm. in twenty-six days. This move- 

 ment of the index is equivalent to 1"045 c.c. absorption. 



Exp. iii. — In order to imitate the conditions of Copeland's 

 experiment more closely, I set up another experiment in which the 

 plaster was confined in four glass tubes, each 16 cm. long and 

 7*5 mm. in diameter. After filling, these tubes were treated as 

 closely as possible according to Copeland's directions, and, having 

 stood in boiled water, were enclosed in a large test-tube of boiled 

 water, fitted with a bung carrying thermometer and capillary as 

 before. The absorption, though slow, apparently on account of the 

 small surface exposed to the water, was easily observable. The 

 absorption continued without appreciable diminution over a very 

 long time. 



The experiment was started December 10th. 



Readings were taken every day ; but it is only requisite to- 

 quote the readings taken when the temperatures were approxi- 

 mately the same. 



These three experiments will serve as examples of many similar^ 

 in all of which plaster of Paris, after being boiled as in Copeland's 

 experiment, shows itself ready to absorb water* I may also state- 



