412 
Phosphorite in Estremadura. 
It may here be traced, either along the surface, or immediately under- 
neath the soil, for a distance of nearly two miles, and in a direction from 
N.N.E. to S.S.W. ; so that, if we may depend upon our own observa- 
tions on this point, it runs conformably to what appears to be the direc- 
tion of the rocks themselves about Logrosan. 
Granting this to be the case, its position* would lead us to regard it 
as interstratified with clay-slate; and we shall therefore venture, in the 
remaining part of this memoir, thus to consider it, although aware that 
it has been spoken of by Le Play as intersecting the formation, and that 
the general direction assigned to the rocks of the country by that geo- 
logist is not in accordance with what appeared to us to belong to those 
immediately around Logrosan. 
At its south-western extremity it seems to terminate not far from the 
base of the granite hill before noticed, but a little to the east of it. 
This hill, indeed, on the side nearest to the phosphorite, consists of 
clay-slate, apparently heaved up by the granite, which constitutes its sum- 
mit, as well as its north-eastern declivity ; but the deposit in question 
has no connexion with the latter rock, as was reported to us at Madrid 
to be the case. 
At this, its south-western termination, the width of the deposit is 
nearly 16 ft. Of its depth we are unable to speak, as it has nowhere 
yet been fathomed to a greater extent than about 10 ft.; but it may be 
inferred, from its being found on the surface for nearly two miles, not- 
withstanding that the country traversed by it presents an undulating 
outline, with alternate elevations and depressions, amounting to at least 
50 ft., that it penetrates to a considerable depth into the substance of the 
rock. 
We traced the course of the mass from this point for about a quarter 
of a mile over a ploughed field, guided by the projecting portions of the 
mineral which protrude at intervals through the vegetable mould, or by 
the fragments of it which have been brought up by the plough. 
We thus followed it up a gentle acclivity, and then again down a 
corresponding descent, till we reached the road leading from Logrosan 
to Guadalupe, where it was first noticed by Bowles. 
Here, as the rock had been already worked, we had the best oppor- 
tunity of examining it ; and accordingly, although we caused excava- 
tions to be made in one or two other places, in order to satisfy ourselves 
that its general characters were the same throughout, yet our knowledge 
of it is principally derived from this one locality. 
In this place it crosses the road obliquely from N.N.E. to S.S.W., 
interstratified with a rock consisting of a compact form of clay-slate, in 
which the slaty cleavage was indistinct, and which is disposed in almost 
vertical strata, inclining however from the granite of the adjoining hill, 
which has been already noticed. 
The width of the phosphorite deposit at this spot is not more than 7 ft. ; 
and it is to be remarked that, out of this mass, the central portion only, 
* We say its position, because its mineral structure and general appear- 
ance certainly give it very much the chaiacter of a vein, as will appear 
from the description given below. 
