SOILS, MANURES, &c. 249 
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period of time, proportionate to that in 
which it has remained under the fait water, 
to recover even the fame degree of fertility 
it polfeffed before the event happened; 
a much longer period than thofe foils 
require which have been laid under water 
by exceffive rains, or which have been 
overflowed by a foft, frefh water river, 
rendered ftill richer at times of flood, 
by the fine earthy particles, falts, &c. 
walhed from the fur face of the adjacent 
lands, by the rains which have caufed it 
to overflow its banks. 
Some foap-makers wafte allies, contain¬ 
ing a certain quantity of vegetable and 
calcareous alkali, were laid in a heap, 
on part of a poor field which had never 
produced any thing but heath, mofs, and 
other aftringent and acetous plants; it 
remained there about a year, and its falts 
deftroyed every plant near it: it was 
K k afterwards 
