On the Nitrate of Soda. 



145 



and millers especially, chew the samples till a stringy, Indian-rubber- 

 like substance remains in the mouth, the quantity of which is their 

 measure of value. This, though unknown to them, is gluten, and ob- 

 tained by a process not very unlike that recommended by Sir H. Davy, 

 who says that the flour should be made into a paste, which is to be cau- 

 tiously washed by kneading under a small stream till all the starch is 

 carried off. 



Thus it seems, then, that the nitrate not only gave an abundant crop, 

 but that the quality, though suffering from accidental injury, when tried 

 by chemical tests was by no means as inferior as its appearance indi- 

 cated ; that, in fact, the flour, containing 5 per cent, more of the most 

 nutritive and wholesome of vegetable substances, would make a greater 

 proportionate quantity of bread, and that, resembling in those qualities 

 the foreign grain of warmer climates sometimes required for peculiar 

 purposes, it may occasionally supersede them. If on future trials these 

 facts should be borne out, and particularly if it should be established 

 that a large proportion of the nitrogen, to which the increased quantity 

 of gluten is owing, is directly afforded by the nitrate, and not by other 

 substances decomposed by the alkali, it cannot be doubted that the use 

 of this manure on wheat will confer an essential benefit on the farmer 

 and the public ; and even should the latter be its mode of operation, it 

 by no means follows that its use may not be attended with much ad- 

 vantage. At all events, the experiment is not without its interest in 

 pointing out chemically the application of one of those manures which 

 supply directly or indirectly the component parts of the plant. On this 

 point generally, and particularly on the effect of ammonia arising from 

 the decay of animal and vegetable manures, and the assimilation of its 

 nitrogen in the plant, the work of Dr. Liebig, cited above, gives much 

 interesting information. He makes it quite clear that the quantity of 

 gluten and albumen will augment when the plant is supplied with an 

 excess of food containing nitrogen ; but he is not quite so satisfactory in 

 his reasonings as to the source of that nitrogen. Drs. Turner and 

 Thomson think that soluble salts are directly absorbed and assimilated 

 as such by plants ; and the latter supports this view by the very conclu- 

 sive evidence that plants near the sea contain soda and common salt, 

 and . inland plants potash : that phosphate of lime is a constant, and 

 phosphate of potash a very common, ingredient in vegetables — nitrate 

 of soda in barley, and nitrate of potash in nettles and the sunflower. 

 He states that experiments made with peculiar salts promote vegetation 

 in peculiar plants— cites Duhamel as proving that sea-plants require 

 common salt, and languish without it, and Bullion as having made seeds 

 of the sunflower grow on a sandy soil containing no trace of nitre, 

 which on examination gave no nitrate of potash, but that the salt made 

 its appearance as usual when the plants were watered with a weak nitrous 

 solution. 



These, and a variety of experiments of a similar sort, lead to the conclu- 

 sion that the nitrate dissolved in water is taken up, and is in itself a part 

 of the food of the plant — a fact which to a certain extent accounts for its 

 luxuriance without any exhausting effect on the soil. Still the circum- 

 stance that the alkali might be disengaged and decompose more rapidly 

 other manures already in the soil, together with the opinion held by 



