104- Chap. XII. Appen&ix, Part 4. No. 1.

husbandman to conduct. Some mention is made, in the lastSection, how this business is generally conducted. In some ofthe best cultivated districts, it is shortly this :—The dung is laidloosely, no cattle allowed to trample upon, and compress it. Itis carried from time to time to the fields, laid in long narrowheaps, repeatedly turned and watered, till it be completely rot-ted ; if not completely so in one season, it lies to rot till thenext. The mark of its being well prepared, is when it can rathdifficulty be lifted on either fork or spade, -j- Thus, the putrefac-tive fermentation is hurried on with the greatest rapidity, andcarried almost to the close of the last stage, which, if there canbe any reliance on the foregoing description of fermentation,must appear to be a very prodigal procedure.

It is not now doubted, that a great proportion of the compo-nent parts of both animals and vegetables is capable of passinginto an aeriform state. When a mass of these substances is laidloose and open, exposed on all sides to the external air, eventhough water be sometimes thrown upon it, 1 that water will part-ly sink to the bottom, and partly be evaporated in the air; andthis agent will always be present, only in the lowest proportion,which is that in which fermentation operates with the greatestviolence, as has been already shown. Through a mass thus ly-ing open, the air impetuously rushes, its oxygen is absorbed,much caloric is liberated, and a violent heat ensues: the com-bination is quickly dissolved: the oxygen combines with the car-bon of the substances, partly to form'carbonic acid gas, whichflies off, partly to form oxid of carbon, which, if not insoluble,is very difficult of solution: the hydrogen is liberated, and, ei-ther combining with oxygen, ascends in steam, as we may see,or with azote, and ascends in volatile alkali, as our senses informus ; and thus the use of a large proportion of the mass is lost.In the mean time, the heat, probabty promoting the combinationof oxygen with some of the hydrogen and carbon of the sub-stances, not disengaged, is forming acids, and these acids com-bining with alkali and earth, forming salts, which, as has beenalready stated, are not the food of plants; and the real food isdissipated in acquiring them.

Some agriculturist, prejudiced in favour of the practice he hasfollowed, which perhaps, on account of other favourable circum-stances, may have been prosperous, may probably read this witha supercilious smile. But since the solution of decayed organizedbodies is the great nourisher of vegetation, to have the com-mand of it in abundance, must be a valuable acquisition to eve-ry cultivator of the ground; and this; a fermentation, accele-rated and carried too far, must consume by perhaps more thana half of what the same substances should have yielded. If any*!pub* of this be still entertained, let a quantity of dry vegeta-

f Report of lioss and Cromarfy.