418 
Phosphorite in Estremadura. 
and the cheapest method would be that of resorting to the bullock 
cars of the country, which are extensively used in Estremadura, 
but only travel in troops together. 
Should, however, the political difficulties, which the Portuguese 
government at j)resent interposes to the transmission of goods by 
the Tagus, be hereafter removed, there seems no reason to doubt, 
but that it might descend that river at certain periods during the 
floods of the winter or of spring. 
But although no prospect can be held out as to this mineral 
being profitably employed as a manure, unless the political condi- 
tion of the Peninsula should become very different from what it 
is at present, and the expense of obtaining bones or other substi- 
tutes for them happen to be greatly augmented, still we do not 
regret having personally examined the locality, both because by so 
doing we have set, as it were, at rest the question that had been 
mooted with respect to the uses to which this material might admit 
of being applied, and also because we have been enabled thereby 
to procure a quantity of it sufficient for making trial of its virtues 
when applied to land capable of deriving benefit from bone 
manure; thus, as we hope, obtaining some data which may 
assist us hereafter in the determination of the interesting problem, 
as to whether the mechanical condition in which mineral sub- 
stances are presented to the secreting organs, exercises any im- 
portant influence upon their adaptation to supply the demands of 
the growing vegetable. 
XXII I. — Instance of the advantage of Subsoil-ploughing, in ad- 
dition to Draining. By George Turner. 
To Philip Pusey, Esq. 
Dear Sir, 
I SEND you a short account of draining and subsoil -ploughing. 
At Michaelmas, 1839, a farm came into my occupation in the 
parish of Cadbury, ten miles from here, on which there was about 
forty acres of land divided into six closes, in a very rough state, 
covered principally with furze, brambles, and rushes, and the 
greater part very wet. The soil, as is often the case in Devon- 
shire, various, but consisting chiefly of about 6 inches of tolerably 
good mould on a rubbly or gravelly clay. I immediately began 
with a field of 6 acres, by cutting drains at various distances, from 
3 to 5 feet deep, according to circumstances, getting, if possible, 
through the clay into the gravelly substance, and filling them to 
within 18 inches of the surface witli well-broken stones, taken 
from a quarry on the farm : and I should here state that the 
