290 TlMEHRI. 
show more plainly than a mere analysis can do what 
constituents would soonest need renewal. For example, 
comparing the potassa with the soda, we find that al- 
though both are present in nearly equal quantity in the 
average soil, the potassa would be removed more than 
eight times as fast as the soda. It will also be evident 
that the chlorine, the potassa, the sulphuric acid, the 
phosphoric acid and the lime are the substances towards 
which attention should be chiefly directed. 
Authorities on agricultural chemistry usually consider 
that the potassa, the phosphoric acid and the lime are 
the principal constituents of soils that stand in need of 
renewal, alleging that chlorine and sulphuric acid are pre- 
sent in sufficient quantity as a general rule. I have shown 
however, that a large proportion of British Guiana soils are 
deficient in both the latter substances, while from the 
analysis of cane ash it will be seen that each of them forms 
an important part of it — sulphuric acid, indeed, being 
present in the ash in greater quantity even than phosphoric 
acid. Therefore, it is evident that the average cane soil of 
the colony requires not only lime, phosphoric acid, and 
probably potassa, but also a due proportion of chlorine 
and sulphuric acid. 
Chlorine can be supplied most cheaply in the form of 
common salt (sodium chloride); or if the soil is deficient 
in potassa, potassium chloride may be used, but it is 
much more expensive. It is usually considered that the 
application of common salt as manure is unadvisable, 
owing to the possibility of its reappearing in the juice, to 
exercise its reputed prejudicial effect on the crystal- 
lisation of the sugar. I am of opinion, however, that no 
