228 SOILS, MANURES, &c. 
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and hardens, as it dries, into a compaft 
folid mafs ; if the foil abounds with clay, 
it will retain water in too great a degree, 
which will rot the fibres of plants ; it will 
be too adhefive to permit their fibres to pafs 
freely into it, and will be difficult to fepa- 
rate or work; the addition of fand, dung, 
or good marie, will obviate thefe effefts, 
and render it of a proper confiftence. 
Sand confifts of fmall cryftalline par¬ 
ticles, and has a contrary effeft to clay 
in any foil where it abounds, permit¬ 
ting water to pafs too freely through 
it; the addition of clay, neat’s-dung, or 
woollen rags, will give it adhefivenefs and 
tenacity, and render it more fertile. 
Sea, or river, fand, is to be preferred 
to that found in ft rata, or beds, in the 
earth, being more free from mineral or 
metallic fubftances, which are pernicious 1 
to vegetation. 
Gravel, 
