SOILS -l I 



J 



Stones. Rub together pieces of stone; the same 

 result will follow, except that the dust will be finer 

 and will be produced with greater difficulty because 

 the stones are harder. Some stones will be found 

 which will grind others without being much affected 

 themselves. 



Rock Salt or Cattle Salt. This is a soft rock, 

 easily broken. Place on a slate or platter one or 

 two pieces about the size of an egg or the size of 

 your fist. Slowly drop water on them till it runs 

 down and partly covers the slate, then set away 

 till the water dries up. Fine particles of salt will 

 be found on the slate wherever the water ran and 

 dried. This is because the water dissolved some of 

 the rock. 



Lime Stone. This is harder. Crush two samples 

 to a fine powder and place one in water and the 

 other in vinegar. Water has apparently no effect 

 on it, but small bubbles are seen to rise from the 

 sample in vinegar. The vinegar which is a weak 

 acid is slowly dissolving the rock. The chemists 

 tell us water will also dissolve the limestone, but 

 very slowly. There are large areas of soil which 

 are the refuse from the dissolving of great masses 

 of limestone. 



We find that the rocks about -us differ in hard- 

 ness : they are ground to powder when rubbed to- 

 gether, some are easily dissolved in water, others 

 are dissolved by weak acids. 



Geologists tell us that the whole crust of the 

 earth was at one time made up of rocks, part of 



