66 ORIGIN AND 



manure depends almost as much on the form 

 in which it is presented to plants, as on the ma- 

 nure itself, it is desirable to notice that nitrogen 

 when combined in this, the liquid state, has lost 

 almost all its tendency to assume its gaseous 

 form, and that it exists in urine in the state of 

 carbonate urate and phosphate of ammonia, in 

 those forms in which it is most easily absorbed 

 and assimilated by plants. 



Another source for the supply of ammonia 

 to the vegetable creation, arises from the gases 

 constantly emitted by volcanoes from their cra- 

 ters, and the fissures in their sides in all parts 

 of the world, and which gases always contain 

 ammonia to a greater or less extent. 



Professor Daubeny supposes this to be one 

 of the principal sources for supplying the in- 

 creased quantity of hydrogen, which a con- 

 stantly increasing number of living animals on 

 the earth's surface must require, and the theory 

 has this peculiar merit, that it obviates the dif- 

 ficulty of supposing the atmosphere to have 

 been charged at any time in excess with this 

 gas, and which excess has been gradually ab- 

 sorbed in the structure of the increased num- 

 ber of living animals, to which civilization has 

 given birth in all parts of the world. It also 

 tends to unite the whole scheme of the creation 

 into one vast whole, and to reconcile our minds 

 to these hitherto mysterious operations of na- 

 ture, by explaining the intimate connexion that 

 exists between volcanoes, and the living orga- 

 nization on the earth's surface. The former of 

 which in their eruptions, and at all times, af- 



