342 SCIENCE OF AGRICULTURE. Part II. 



matter disengaged in fermentation, it grew with much more luxuriance than the grass in 

 any other part of the garden. Besides the dissipation of gaseous matter, when ferment- 

 ation is pushed to the extreme, there is another disadvantage in the loss of heat, which, 

 if excited in the soil, is useful in promoting the germination of the seed, and in assisting 

 the plant in the first stage of its growth, when it is most feeble and most liable to disease ; 

 and the fermentation of manure in the soil must be particularly favourable to the wheat 

 crop, in preserving a genial temperature beneath the surface late in autumn and during 

 winter. Again, it is a general principle in chemistry, that, in all cases of decomposition, 

 substances combine much more readily at the moment of their disengagement, than after 

 they have been perfectly formed. Now, in fermentation beneath the soil, the fluid matter 

 produced is applied instantly, even whilst it is warm, to the organs of the plant, and 

 consequently is more likely to be efficient, than that from manure which has gone through 

 the process, and of which all the principles have entered into new combinations. 



2273. Checkiyig fermentation by covering. " There are reasons sufficiently strong," 

 Grisenthwaite observes, " to discourage the practice of allowing dung heaps to ferment 

 and rot without interruption. It appears that public opinion has slowly adopted the 

 decisions of chemical reasoning, and dung-pies, as they are called, have been formed with 

 a view to save what was before lostj a stratum of mould, sustaining the heap, being 

 placed to receive the fluid parts, and a covering of mould being applied to prevent the 

 dissipation of the aerial or gaseous products. These purposes and contrivances, unfor- 

 tunately, like many of the other operations of husbandry, were not directed by scientific 

 knowledge. To cover is so commonly believed to confine, that there is no wonder that 

 the practical cultivator adopted it in this instance from such a consideration ; but it is in 

 vain ; the elasticity of the gases generated is such as no covering whatever could pos- 

 sibly confine. If it were perfectly compact, it could only preserve as much carbonic 

 acid as is equal to the volume or bulk of air within it ; a quantity too inconsiderable to 

 be regarded, could it even be saved : but every particle of it must be disengaged, and 

 lost, when the covering is removed." 



2274. Checking fermentation by watering is sometimes recommended; but this prac- 

 tice is inconsistent with just chemical views. It may cool the dung for a short time; but 

 moisture, as before stated, is a principal agent in all processes of decomposition. Dry 

 fibrous matter will never ferment. Water is as necessary as air to the process ; and to 

 supply it to fermenting dung, is to supply an agent which will hasten its decay. In all 

 cases when dung is fermenting, there are simple tests by which the rapidity of the pro- 

 cess, and consequently the injury done, may be discovered. If a thermometer, plunged 

 into the dung, does not rise to above one hundred degrees of Fahrenheit, there is little 

 danger of much aeriform matter flying off. If the temperature is higher, the dung 

 should be immediately spread abroad. When a piece of paper, moistened in muriatic 

 acid, held over the steams arising from a dunghill, gives dense fumes, it is a certain test 

 that the decomposition is going too far ; for this indicates that volatile alkali is dis- 



2275. In favour of the application offarm-yard dung in a recent state, a great variety of 

 arguments may be found in the writings of scientific agriculturists ; but the practice of 

 the best farmers, both in Scotland and in the Netherlands and other parts of the Conti- 

 nent, is against the theory. 



2276. Farm-yard manure in Scotland is never laid on the ground without being more or less prepared. 

 For turnips it is regularly removed from the fold or stable yard before the middle or end of April. It is 

 then laid up in a regular heap on a secluded spot of ground, generally in one corner of the field, not much 

 exposed to wind, or liable to be flooded by water. The height of the heap should seldom be less than from 

 4 to 4| feet, and its breadth, for the convenience of being turned over when necessary, and on other 

 accounts, may be about two thirds of its length, sufficiently broad at least to admit two carts or more to be 

 loaded at a time, as may be necessary ; and great care should be taken, not to put either horse or 

 cart upon it, which is easily avoided, by backing the cart to the pile, and laying tlie dung compactly 

 together with a dung fork. It is not unusual to cover the dunghill with a coat of earth or moss, which 

 keeps in the moisture, and prevents the sun and wind from doing injury, by evaporating those fluid sub- 

 stances, which arise from a valuable part of the dung. Dung, when managed in this manner, generally 

 ferments very rapidly ; but if it is discovered to be in a backward state, it is turned over about the first of 

 May, when the weather becomes warm ; and the better it is shaken about and mixed, the sooner will the 

 object in view be accomplished. {Gen. Rep. Scot. vol. ii.) For wheat crops sown on fallow in autumn, or 

 for beans, potatoes, or other crops sown or planted in spring, the farm or fold yard manure is carried out at 

 different times, during the preceding summer and winter, and formed into large dunghills in the fields 

 where they are to be used. These dunghills are turned once or twice, and moistened by watering, or 

 covered by earth or moss, so as to accelerate or retard the fermentation, according to the period when the 

 material may be wanted for use. The test of their fitness for this purpose is that degree of tenderness 

 which admits of the easy separation of the littery parts when a dung fork is inserted and a forkful 

 taken up. 



2277. The doctrine of the proper application of manures from organised substances, 

 offers an illustration of an impoilant part of the economy of nature, and of the happy 

 order in which it is arranged. The death and decay of animal substances tend to 

 resolve organised forms into chemical constituents ; and the pernicious effluvia disen- 

 gaged in tlie process seem to point out the propriety of burying them in the soil, where 

 they are fitted to become the food of vegetables. The fermentation and putrefaction of 



