Book III. SPECIES OF MANURES. S29 



prevented as much as possible ; and tlie only cases In which these processes can be useftil, 

 are when the manure consists principally of vegetable or animal fibre. The circum- 

 stances necessary for the putrefaction of animal substances are similar to those required 

 for the fermentation of vegetable substances ; a temperature above the freezing point, the 

 presence of water, and the presence of oxygen, at least In the first stage of the process. 

 To prevent manures from decomposing, they should be preserved dry, defended from the 

 contact of air, and kept as cool as possible. Salt and alcohol appear to owe their 

 powers of preserving animal and vegetable substances to their attraction for water, by 

 which they prevent its decomposing action, and likewise to their excluding air. 



SuBSECT. 2. Of the different Species of Manures of Animal and Vegetable Origin. 



2169. The properties and nature of the manures in common use should be known to 

 every cultivator : for as different manures contain different proportions of the elements 

 necessary to vegetation, so they require a different treatment to enable them to produce 

 their full effects in culture. 



21 70. All green succulent plants contain saccharine or mucilaginous matter, with woody 

 fibre, and readily ferment. They cannot, therefore, If intended for manure, be used too 

 soon after their death. Hence the advantage of digging or ploughing In green crops, 

 whether natural, of weeds, or sown on purpose ; they must not, however, be turned in too 

 deep, otherwise, as Mrs. Ibbetson has shown (Philos. Mag. 1816), fermentation will be 

 prevented by compression and exclusion of air. , Green crops should be ploughed in, if it 

 be possible, when in flower, or at the time the flower Is beginning to appear, for it is at 

 this period that they contain the largest quantity of easily soluble matter, and that their 

 leaves are most active in forming nutritive matter. Green crops, pond-weeds, the paring 

 of hedges or ditches, or any kind of fresh vegetable matter, require no preparation to fit 

 them for manure. The decomposition slowly proceeds beneath the soil; the soluble mat- 

 ters are gradually dissolved, and the slight fermentation that goes on, checked by the want 

 of a free communication of air, tends to render the woody fibre soluble without occasion- 

 ing the rapid dissipation of elastic matter. When old pastures are broken up and made 

 arable, not only has the soil been enriched by the death and slow decay of the plants 

 which have left soluble matters in the soil, but the leaves and roots of the grasses, living 

 at the time, and occupying so large a part of the surface, afford saccharine, mucilagin- 

 ous, and extractive matters, which become immediately the food of the crop, and the 

 gradual decomposition affords a supply for successive years. 



2171. Rape-cake, which is used with great success as manure, contains a large quantity 

 of mucilage, some albuminous matter, and a small quantity of oil. This manure should 

 be used recent, and kept as dry as possible before it is applied. It forms an excellent 

 dressing for turnip crops ; and is most economically applied by being thrown Into the soil 

 at the same time with the seed. 



2172. Malt-dust consists chiefly of the infant radicle separatcid from the grain. Sir 

 H. Davy never made any experiment upon this manure ; but has great reason to suppose 

 it must contain saccharine matter, and this will account for its powerful effects. Like 

 rape-cake, It should be used as dry as possible, and Its fermentation prevented. 



2173. Linseed-cake Is too valuable as a food for cattle to be much employed as a 

 manure. The water in which flax and hemp are steeped, for the purpose of obtaining 

 the pure vegetable fibre, has considerable fertilising powers. It appears to contain a 

 substance analogous to albumen, and likewise much vegetable extractive matter. It 

 putrlfies very readily. By the watering process, a certain degree of fermentation is ab- 

 solutely necessary to obtain the flax and hemp In a proper state ; the water to which they 

 have been exposed should therefore be used as a manure as soon as the vegetable fibre 

 is removed from it. Washing with soap has been successfidly substituted for watering 

 by lie. 



2174. Sea-weeds, consisting of different species of fuel, algse, and confervae, are much 

 used as a manure on the sea-coasts of Britain and Ireland. By digesting the common 

 fucus, which is the sea-weed usually most abundant on the coast, in boiling water, one- 

 eighth of a gelatinous substance, will be obtained, with characters similar to mucilage. A 

 quantity distilled gave nearly four fifths of its weight of water, but no ammonia ; the 

 water had an empyreumatic and slightly sour taste ; the ashes contained sea-salt, car- 

 bonate of soda, and carbonaceous matter. The gaseous matter afforded was small in 

 quantity, principally carbonic acid, and gaseous oxide of carbon, with a little hydro-car- 

 bonate. This manure is transient In its effects, and does not last for more than a single 

 crop ; which Is easily accounted for from the large quantity of water, or the elements of 

 water, it contains. It decays without producing heat when exposed to the atmosphere, 

 and seems, as It were, to melt down and dissolve away. A large heap has been entirely 

 destroyed in less than tWo years, nothing remaining but a little black fibrous matter. 

 Some of the firmest part of a fucus were suffered to remain in a close jar, containing at- 

 mospheric air for a fortnight : in this time it had become very much shrivelled ; the sides 



