"Now, this may be done on the skirt of any wood where the matters are all at hand. This mode is far preferable to the _above ground_ burning in _heaps_. Because in the next place, the _smoke escapes there_, which is the finest part of the burnt matter. _Soot_, we know well, is more powerful than ashes, and, soot is composed of the _grossest parts of the smoke_. That which flies out of the chimney is the best part of all.
"In case of a want of wood wherewith to begin the fire, the fire may be lighted precisely as in the case of _paring and burning_. If the kiln be large, the oblong square is the best figure.--About _ten feet wide_, because then a man can fling the earth easily over every part. The mode they pursue in England when there is no _wood_, is to make a sort of building in the kiln with turfs and leave air holes at the corners of the walls, till the fire be well begun. But this is tedious work; and is in this country wholly unnecessary. Care must, however, be taken, that the fire be well lighted. The matter put in _at first_ should be such as is of the lightest description; so that a body of earth on fire may be obtained, before it be too heavily loaded.
"The burning being completed, having got the quantity you want, let the kiln remain. The fire will continue to work, until all is ashes. If you want _use_ the ashes sooner, open the kiln. They will be cold enough to remove in a week."
A practice has long prevailed in Europe of paring and burning soils for the purpose of improving their texture and increasing their fertility. On clay lands, and such as contain too much vegetable matter, we conceive the process might be advisable if not too expensive. Its effect on clays is to destroy the adhesive quality of the soil, as the earth burned becomes rather of a silicious texture; and at the same time the surface is much enriched by the operation. In the other case it is calculated to reduce the redundancy of vegetable matter, as well as to enrich the soil. The operation is performed in the following manner:
When the ground is in a good sward of grass let it be carefully turned over with the plough, the irons of which should be well sharpened. Let the plough run about three inches deep.--Then cross plough with a very sharp coulter, and the sward will all be cut into squares of about 10 or 12 inches. You then proceed to set these square chunks up edgeways, by leaning two together, in which situation they will soon dry.--When well dried build a part of them tip in the form of little ovens, and let this be done at the distance of about every 18 feet each way. These are all to have a little opening or door, at a common windward side, for the air to enter, and another opening above for the smoke to pass off. On some dry day when the wind is fair for blowing into the holes below place some straw or other dry rubbish into the holes and set fire to it. As soon as the fires have got fully going in each of the heaps, let the holes in the tops be stopped up, for the purpose of retaining the smoke, and keep gradually building up the heaps as the fire penetrates them, until all the chunks of earth are piled up round them; and when the heaps have fully burned and sufficiently cooled, they are to be evenly spread over the ground, and ploughed in.