80 Recent Publications on Manures. 



was sifted on, was so great, that it could be told at many yards 

 distance where the soot ended, by the strength of the onions 

 being so much greater. Mi*. Adam, in the Quarterly Journal of 

 Agriculture last year, in trials with many different kinds of ma- 

 nures, all the new kinds, found the soot much the cheapest, and 

 the crops of grain very superior. Like the nitrates, however, 

 and other concentrated manures, it will not do if in excess ; and 

 when the plants are growing, the time of rain should always be 

 chosen to spread it among the plants : when washed into the 

 soil, divided and diluted, it produces most benefit, but is apt 

 to kill the leaves if the weather is dry ; I have seen onions 

 killed with it in dry weather. Cow urine is another powerful 

 manure: if applied to cauliflowers in wet weather, it produces 

 great effect; if applied in dry weather, it generally kills the plant. 

 Some unaccountable results are often produced also by the best 

 of manures, and show the necessity of repeated experiments. 

 Sir Humphry Davy found that nitrate of ammonia, applied in 

 solution to grass, produced no effect, while nitrate of soda on 

 the same piece close at hand did : he expresses astonishment at 

 the result himself, but it does not appear that he repeated it. 

 Others who have tried the nitrate of ammonia say that it has 

 produced great effects : it is not yet an article of commerce as a 

 manure, but, from the great quantity of nitrogen contained, 

 should be very beneficial. Professor Dumas says it is always 

 the product of electric storms. In trials for experiments, if 

 there are any of the pieces of the soil experimented on abounding 

 in oxides of iron, they may, from their great affinity for acids, 

 when in the state of protoxide, decompose the salts ; and from 

 their tendency to assume again the state of peroxides, which do 

 not retain the acid, the nitric acid may be given off again to the 

 air and lost. If the proper proportions of food and light are 

 wanting, experiments may give a different result from what 

 they would have done if these were all present. Heavy washing 

 rains may carry off top-dressings ; and the above and many 

 other unobserved circumstances may derange the effects of ex- 

 periments ; and we may see here the necessity of frequently 

 repeated trials, and on a large scale, before we can decide on 

 the comparative benefit of manures. From what has been stated 

 on the nitrates, ammonia, &c, we may infer, that, though nitrogen 

 is needed as a constituent, yet it is also much needed as a stimu- 

 lant, as it is to be found in the latex 01 circulating fluid of the 

 plant, in the state of ammonia, wherever life is most active ; sti- 

 mulating the action of the organs, and assisting in the decompo- 

 sition of the food needed to supply every constituent where 

 wanted, and giving the deep green healthy colour of luxuriant 

 vegetation. If this is accompanied by light and heat, and a 

 proper proportion of the other constituents of the food of plants, 



