116 CAPILLARY ATTRACTION. SECT. XIV. 



brought into collision by this principle. But two balls, one of 

 which is wet and the other dry, repel one another as soon as the 

 liquid which separates them is curved at its surface. A bit of 

 tea-leaf is attracted by the edge of the cup if wet, and repelled 

 when dry, provided it be not too far from the edge and the cup 

 moderately full ; if too full, the contrary takes place. It is 

 probable that the rise of the sap in vegetables is in some degree 

 owing to capillarity . 



