24 EFFECT OF WATER ON ROCK POWDERS. 



the action of wet grinding. The word "pectoid" is recommended to 

 describe the condition of the particles as being more appropriate to 

 the connection in which it is used than the words "colloid" or 

 "hydrogel." 



(7) The absorption of the bases known to take place when certain 

 clays are treated with dilute salt solutions is explained by means of 

 the colloid theory, as is also their increase of binding power under the 

 action of water and certain solutions. 



(8) The possibility of rendering the potash contained in rocks avail- 

 able as a fertilizer is suggested. 



