GROWTH 13 



water is not absorbed in quite the same 

 manner in the two cases. Absorption 

 of water may occur in two ways, which 

 are known as imbibition and osmosis. 

 Imbibition is the process which occurs 

 when a piece of dry wood is placed in 

 water. The water is taken up into mi- 

 nute pores, other processes follow, and 

 the result is a swelling which, though 

 short-lived, can develop great pressure. 

 At one time granite blocks were split 

 open by drilling holes in a straight line 

 and inserting plugs of dry wood. These 

 were covered with wet rags, the wood 

 absorbed water and the granite block 

 was split. Careful measurements show 

 that starch may develop a pressure of 

 thirty thousand pounds per square inch 

 in taking up water. It is therefore no 

 wonder that a ship loaded with rice is 

 quickly burst asunder if water reaches 

 the cargo. 



In osmosis water is absorbed in a dif- 

 ferent way. This may be illustrated by 

 the story of the good abbe who hid a 



