378 



Nitrate of Soda as a Manure. 



are rendered fertile for ages by patriot blood, we now understand 

 scientifically this mournful memorial of human slaughter. 



The admission of this truth has been delayed, according to 

 Dr. Wilson, by " a reluctance in teachers of chemistry to admit 

 two sources ojf nitrogen for plants, because it complicates their 

 statements and multiplies their formulae." The awkwardness is 

 no doubt the greater, because the substances in question are not 

 merely duplicate, but of opposite natures; the one, ammonia, being 

 alkaline, and the other acid. Dr. Wilson suggests, not unjocosely, 

 that the exclusive advocates of ammonia should assume the con- 

 version of the nitric acid into ammonia before any organic com- 

 pound is developed, and thereafter carry out the ammonia theory 

 as before.* On the other hand, the distinguished chemist of 

 Cirencester College, Dr. Voelcker, informs me that, in his opinion, 

 " plants in general are more dependent upon nitric acid, as the 

 source from which they derive their nitrogen, than upon am- 

 monia." Within soils containing lime — and most soils contain 

 lime, either natural or applied — Dr. Voelcker thinks that nitro- 

 genous manures are converted not into ammonia, but into nitric 

 acid. Now, of the manures above enumerated, two only are 

 strictly ammoniacal, namely, soot and gas liquor. Of the others, 

 in some, such as fish, rags, &c., the Nitrogen is as yet unde- 

 veloped, and may therefore assume in the soil the form either of 

 ammonia or nitric acid, we know not which. In fresh dung and 

 urine it is mainly undeveloped. Even in guano. Dr. Voelcker has 

 found it developed only to the extent of one quarter. But in all 

 these cases he conceives the undeveloped Nitrogen to be changed 

 within suitable soils into Nitric acid. Further investigation is 

 evidently required. The general law is established as to nitro- 



" Emathia, Heaven decreed, was twice imbrued, 

 And Hsemus' fields twice fatten'd with our blood." 



Georgics: Wartox. 



Lucan also, in speaking of the same battle-field of Pharsalia, mentions the 

 darker hue imparted to the young corn by past bloodshed, as well as the remains 

 of fallen warriors turned up by the plough : — 



" Quse seges infectanon surget decolor herba? 

 Quo non Eomanos violabis vomere Manes?" — Pharsalia, vii. 



* Dr. Hartstein, Director of the Prussian Agricultural College at Poppeldorf, 

 in an able work he has just published on the ' Improvements of English and Scotch 

 Tarming,' argues earnestly for this previous conversion of nitric acid into ammonia. 

 *' This occurs," he says, "as follows: — The hydrogen liberated by the decom- 

 position of organic substances, when it meets the nitric acid of saltpetre, not only 

 withdraws from it oxygen, and so forms water, but, further, hydrogen in the 

 nascent state combines with the nitrogen, foi-ming ammonia, the food of plants. In 

 thus explaining the beneficial action of saltpetre, we find no scientific contradic- 

 tion. The transformation of nitric acid into ammonia by hydrogen, when this 

 latter substance is liberated from combination, and comes simultaneously into con- 

 tact with nitric acid, is a well-known fact." — Fortschritte cler Englischen und Schot- 

 tischen Landv:erthschaft, von Dr. Edward Hartstein. Bonn. IS 53. 



