402 Horticultural Chemistry. 



riant on ground manured with sprats, than on that manured 

 with the dung of horses, and both these superior to the same 

 crop" grown on a plot manured with the decayed parts of its 

 own species? Apparently, because the manures mentioned 

 decompose with a rapidity exactly proportioned to the order 

 of benefit. Sprats decompose, and their parts become soluble 

 and capable of introsusception, first and most rapidly ; then 

 the dung of animals ; lastly, the vegetable remains. All the 

 less solid animal matters decompose with greater rapidity than 

 vegetable matters : hence the dung of such animals as are car- 

 nivorous is the most prompt in benefiting vegetation ; witness 

 night soil, pig's dung, &c. ; but such manures are not the most 

 permanent. Hassenfratz manured two portions of the same 

 soil, No. 1. with a mixture of dung and straw highly putrefied ; 

 No. 2. with a similar mixture, newly made. He observed that 

 during the first year the plants in No. 1. produced the best 

 crop, but the second year (no more dung being added) 

 No. 2. produced the best crop ; the result was the same the 

 third year, after which both seemed alike exhausted. (Ann. 

 de Chimie, xiv. 57.) The same chemist found that a soil 

 manured with wood shavings did not, during the two succeed- 

 ing years, produce a superior vegetation than the same soil 

 without any manure ; the third year, however, it was better, 

 nor was it until the fifth year that it reached the maximum of 

 fertility. The site of a wood-stack and the newly cleared 

 lands of America are eminently fertile, from the gradually 

 decomposing vegetable remains they contain. 



These facts and observations teach us that the most prompt 

 manures are the reverse of being economical : vegetable re- 

 mains, incorporated with a soil, will insure an average pro- 

 duce during several years ; animal matters and dungs 

 highly putrescent are powerfully but transiently beneficial. 

 Putrefaction is evidently the means of rendering these sub- 

 stances available to plants ; hence thoroughly decayed stable 

 manure is usually employed by gardeners, as being of imme- 

 diate benefit, admitting of clean husbandry, and as economy 

 is not in private establishments the general presiding genius 

 of the gardens. If stable dung or other manure is allowed 

 to putrefy in an unenclosed heap, the loss is immense ; all the 

 gases which pass off during decomposition, all the soluble 

 matters which drain away, are highly nutritious to plants, as 

 has been proved by Davy and others. If the decomposition 

 is thus allowed to proceed, until the heap becomes a sapona- 

 ceous mass, the loss cannot be less than 50 per cent. Not- 

 withstanding all the reasoning of chemists* however, putrefied 



