72 



CHEMISTRY, GEOLOGY 



Fig. 21. 



coarse, mossy grass-lands ; and in large quanti- 

 ties on peaty soils, or those containing an excess 

 of organic matter. 



Mixed with earth or vegetable matter, or with 

 animal substances, as fish, whale-blubber, etc., 

 they will often be found a very useful compost. 



If you want to ascertain 

 whether a soil or substance 

 contains lime, you may pour 

 upon a small quantity of it vin- 

 egar, or dilute muriatic acid. 

 If lime is present, the mixture 

 will froth up, or effervesce. 

 This bubbling, or effervescence, 

 is caused by an escape of the 

 carbonic acid of the carbonate 

 of lime, because the stronger 

 acids combine with the lime, 

 and therefore let the carbonic 

 acid free. 



You may easily prove this 

 by putting a little marl, or 



Questions. On what lands is carbonate of lime most 

 useful ? How can you ascertain if a soil contains lime ? 

 What makes the frothing, or efferTescence ? How may 

 you know that carbonic acid gas is liberated ? 



