SOILS, MANURES, &c. 243 
Upon calcining one of thefe malfes, 
and reducing it to powder, if a magnet 
be applied, it will attra£l and feparate 
numerous particles of iron. 
The belt method of converting foils 
of the above defcription to a ftate of 
fertility is as follows: 
Spread a fufficient quantity of quick 
lime on the furface ; let it have a con- 
fiderable time to operate, and afterwards 
frequently turn up the foil and lime 
incorporated together, that the air may 
pervade it thoroughly ; by this means its 
malfes will be reduced, and their metal- 
✓ 
lie properties deftroyed ; the foil will 
finally become produftive. 
If neutral falts abound in any foil, to 
fo great a degree as to become noxious 
to vegetation, it may be known by the 
following experiment. 
Boil 
1 
