278 FIRESIDE SCIENCE. 



The amount of phosphorus or phosphoric acid 

 in the soil is usually insufficient to meet the wants 

 of the plant, and hence the farmer must furnish 

 supplies if he wishes to increase his crops. For- 

 merly there were but two sources of supply, that 

 from manure or animal excrement, and that from 

 the bones of animals ; but now we have a third 

 source in the mineral coprolites, or phosphatic de- 

 posits, found upon the coast of South Carolina. 

 From these substances what are popularly known 

 as superphosphates are made and sold largely in 

 the market. 



Potash holds a most important place in the list 

 of substances consumed by plants, and hitherto 

 much anxiety has been manifested regarding a sup- 

 ply equal to our wants. A few years ago we were 

 acquainted with no sources of the agent save that 

 of the ash of plants, and as mineral coal came into 

 use for furnishing household warmth, wood ashes 

 and the potash salts obtained from them became 

 very scarce and costlv. Every year the farmer 

 removed from the soil large quantities of potash in 

 his crops, which he could not return again through 

 the excrement of his animals, and therefore it was 

 evident his lands were becoming impoverished to 

 an alarming extent. High cultivation, as respects 

 potash, increases this impoverishment, as all culti- 

 vated plants are richer in this substance than those 



