Page:Encyclopædia Britannica, first edition - Volume I, A-B.pdf/74

 A G R I C U L T U R E. and to communicate to It as high a degree of an abforb- fame manner upon the foil. They communicate to the foil a power of attradling the vegetable food from the ing quality as it is capable of receiving. Thefe different operations of lime is confirmed by air, diflblve the vegetable food, and prepare it for enexperience, and agreeable to the pfa&ice in thofe parts of tering the roots of plants. They likewife attradt oils Scotland where lime is moft ufed. When employed for fo ftrongly, that they are frequently ufed for extracting the purpofe of improving barren lands, it is laid on in greafy fpots out of cloth; they are therefore fuppofed to large quantities, to give a flimulus to the foil, and make attract oil from the air and earth, which is the chief init exert all its vigour; and when applied to land already gredient in the nourifhment of plants. improved, it is ufed in fmall quantities, and repeated Both the clay and ftone marks are long of diffolving. once every third or fourth year, to prevent too great Large pieces of the ftone-mark are fometimes found unan exertion, and impoveriiliing the land, by exhauft- difiblved many years after'it has been laid on the land This renders it neceffary to lay on a large quantity o. ing too much of the vegetable food. The lands in Scotland capable of the greatefi: im- them, left their effedts Ihould not at firft appear. provement by lime, are the out-field and muir lands. As mark may ‘be ufed with fafety in greater quantiThe out-field land is generally kept three years in tillage, ty than lime, it muft communicate to the foil a ftronger and carries three crops of oats ; it is then allowed to power of attracting the vegetable food, and confequently reft fix years, and after that is brought again into tillage. it ought always to be preferred. Mark is likewife preThis method of cultivating out-field land is found, by ferable to lime in this refpedt, that it is longer of diffolcalculation, to be fufficiently able to bear the expence, ving; and therefore the land will continue to carry betand allow a reafonable profit to the farmer, befides the ter crops for feveral years longer after it has been marled. improvement the lands derive from the lime. However, if the foil be foft and fpungy, the mark, like Is England, lime is fometimes ufed as a top dreffing lime, will fink below the reach of the plough, and prefor wheat. The method is this: They fow their wheat vent thofe advantages which might naturally be expecced without laying on any manure ; and in the beginning of from it. February, for every acre of land, they take 20 bulhels of Though marie is preferable to lime as a manure; yet it unflaked lime, and 4 bufhels of fand, or brick-rubbilh. muft be confidered, that their operation upon the earth Towards the end of the month, the lime is flaked and is the fame; confequently, when markd land has been mixed with the fand: In the laft week of the month, this exhaufted with crops, it cannot receive much benefit is fcattered by way of top-drefling over the green wheat; from an immediate application of mark a fecond time; and as rain generally fucceeds, it is foon waflied down for the fame reafon, it can receive as little advantage from to the roots of the plant, and gives them a vigour and lime : Dung therefore, as it contains a great proporftrength of grov/yh that is aftonifhing to people who have tion of the vegetable food, which lime and marks diminever feen this method pradfifed. But, if the weather nifh, is the moft proper manure for markd or limed inclines to be dry, the quantity of fand muft be doubled, lands exhaufted with crops. to prevent the plants from being burnt by the corrofive What was faid with regard to the application of lime, quality of the lime. in fmaller or larger quantities, to barren lands and lands in good o^'er, may be faid with equal propriety with regard to ftone and clay marks. Of Maries. The general characters by which marie is beft diftinOf Shell-marle. guilhed, are thefe : It attracts and ferments with acids, and does not bake in the fire like potter’s earth, which This mark is of a different nature from the ftone diftinguiflies it fufficiently from clay; upon being expo- and clay marks. It does not diffolve with water, but fed for fome time to the air and weather, it diflblves like abforbs and fwells with it like .a fpunge: It attracts acids qmck-lime, and falls intp a fine powder; when dry, it more forcibly. But the principal difference betwixt the is friable and undtuous like lead-ore ; when wet, it is (hell-mark and the other marks confifts in this, that foft and flippery to the touch; whereas virgin-earth the (hell-mark contains a great quantity of oil. is rough and gritty. .This mark is therefore luppofed to promote vegetaThere are a great variety of marks ; but they are by increafing the food of plants, by communicating x generally reduced to three kinds: The clay, the ftone, tion, to the foil a power of attracting this food from the air, and the fhell marie. by dividing foil into fmall particles, and by preparing The clay and ftone marks are nearly of the fame na- the vegetablethefood for being abforbed by their roots. ture ; but the fliell-maile differs from both. As (hell-mark does not exhauft land like lime and the other marks, it may be repeated as often as the hufbandman pleafes. Its effects are likewife more fudden. Of Clay and Stone Maries. Though plants will not grow in thefe marks, when Of Apes. pure; yet, when mixed with foil, they become an excellent manure. The afhes of vegetables contain a large quantity of Stone and clay marks are poffeffed of much the fame alkaline Hence they attraCt acids more ftrongly qualities with lime, anfl confequently aft nearly in the than anyfait: other fubftances. The 49