■ 



••x, 







uifl 



' fluid 



^^ttiabi 



e 



i^atte 



r 



^^^Wi 



or 



' or Mith 

 '-^ »ew Cora. 



Sulphuric. 



hur 



c 



rformed very 

 ig of a dung- 

 :5 of the hot- 

 le decompof- 



heat Is given 

 ood alone, 



ifiuch ligbt is 

 ply to tiie 



.1 w 



im 



h other bodies 



; heat or ligb^ 



^s, as oxygen 



converts 



the * 



ndtb^ 



as 



hur; 



a 



ances 



pither 

 tallic 



le 



are p^^' 



bodi^^ 



c 



1 CO 



mriioi^ 



Of5 



> 



an 



rci 



oECT» A. • 2. ^« 



MANURES. 



193 



red ochre of 



w 



ch h 



obtained the name of acid 



but 



d oxydes of thofe 



th 



Now it happens, that none of thefe bafes, which can combine 

 oxvsen aione, are foluble in water, and therefore can not be 

 imbibed by the abforbent veffels of vegetable roots, until they become 

 acids ; and are perhaps then all of them in greater or lefs quantities 

 foluble in water ; and are thence capable of being drank up by the ab- 

 forbent vedels of vegetable roots, and conftitute a part of the food of 



plants. 



5. When vegetable fubflances are decompofed by fermentation, 



there is a quick union of oxygen and carbon ; and this carbonic acid 

 gas, called formerly fixed air, rifes up in vapour, and flies away. 

 But where this procefs goes on more flovvly, as in a dung-hill lately 

 turned over, or in black garden mould lately turned over, and thus 

 expofed to the air ; much of which' remains in the cells or cavities 

 of the hotbed, or border ; this carbonic acid is fiowly produced, and is 

 abforbed by vegetable roots, I fuppofe in its fluid ftate, or diflolved 

 in water, before it acquires fo much heat as to rife in the atmofphere 

 in the form of gas. 



This carbonic gas in its fluid flate, or diflolved in water, not in its 

 aerial or gafleous flate, is the principal food of plants ; as appears, 

 becaufe their folid fibres confift principally of carbon, and their fluids 

 of water. 



6. Next to carbonic acid the aqueous acid, if it may be fo called, or 

 water, fecms to aflbrd the principal food of vegetables; as water con- 

 fifts of oxygen and hydrogen, it is properly an acid, like all other com- 

 binations of oxygen ; and when abforbed by vegetable roots becomes 

 in part decompofed in the circulation or fecretion of their juices ; 

 the oxygen difappears, or contributes to form the vegetable acids ; 

 and the hydrogen produces ammonia by its union with azote ; which 

 may contribute to vegetable nutriment by its mixture with oils, and 

 thus producing foaps, which become difFufible in water ; and alfo by 



decompofing 



\ 



Cc 



^ 



