Nitrate of Soda as a Manure. 



375 



Still the question has remained open, and the highest chemical 

 authority in Edinburgh has recently questioned the manuring 

 power of nitric acid ; nor can any one blame that distinguislied 

 philosopher, Dr. Gregory, for exercising caution in admitting 

 such an hypothesis. For if it be true that all substances con- 

 taining nitrogen, in whatever form, are thereby constituted ma- 

 nures, this will not be a mere rule of farming, but an impor- 

 tant law of Vegetable Physiology : the more important, perhaps, 

 because we hardly know any other law under which vegetables 

 acquire their substance, excepting that by which they absorb car- 

 bonic acid in daylight. Indeed, his opponent, Dr. Wilson, in 

 an able paper* read before the Royal Society of Edinburgh last 

 spring, advocated the efficiency of nitric acid w4th some hesitancy, 

 admitting that " soda might be the more important constituent of 

 nitrate of soda considered as a fertilizer." So long, then, as the 

 productive power of nitric acid rested upon abstract reasoning, 

 however cogent, the general law could not be regarded as finally 

 valid. It appeared, therefore, desirable to bring the matter to a 

 decisive experiment, and by employing the two elements of 

 Nitrate of Soda, the acid and the alkali, separately, to ascertain 

 in which of the two the manuring virtue is seated. It would be 

 scarcely possible, of course, to use nitric acid upon acres of land, 

 nor did it seem necessary, for we know the vivid green and the 

 rapid growth induced upon grass by nitrate of soda. Whichever, 

 therefore, of its two elements used side by side with itself, the 

 alkali or the acid, produced the same vivid green and the same 

 rapid growth, must clearly be the active principle of the com- 

 bined salt. 



In applying nitric acid for the first time as a manure, whatever 

 confidence one might entertain in a scientific induction, one could 

 not see the most powerful of acids eating away the very spoon which 

 held it, or feel its acrid fumes in the lungs, without some mis- 

 giving as to its action upon the tender spongioles of the grass's roots. 

 Considerable dilution was of course necessary, and the first point 

 to be ascertained was the amount of water required to be mixed 

 with the acid for the safety of the living fibres. Six stripes, then, 

 -each five feet long and one broad, having been marked out by pegs 

 upon a grass-plot, these received severally from a watering-pot a 

 pint and a half of water containing nitric acid, the proportion of 

 which was successively decreased. Two other stripes also re- 

 ceived nitrate of soda in different quantities. The three strongest 

 ■doses of nitric acid had burnt up the growing grass by the follow- 

 ing morning, but, to my great satisfaction, in about a week the next 

 stripe showed unequivocal marks of benefit from the nitric acid. 



* Transactions of the Eoyal Society of Edinburgh, xx. 41, read April ISth. 



