408 
Phosphorite in Estremadura. 
Proust then introduces a passage, which is probably the one 
that has given rise to all the exaggerated statements handed on 
from one writer to another respecting this mineral, 
" The stone," he says, occurs, not in veins, but in entire 
hills (collados enteros) in the vicinity of Logrosan, a village be- 
longing to the jurisdiction of Truxillo, in the province of Estre- 
madura. The houses and the walls which inclose the fields are 
built of it." To this however he appends a remark, which, by 
showing that his preceding statement was based on hearsay evi- 
dence only, ought to have suggested some caution as to the degree 
of credit which deserved to be attached to it. 
" But," he says, " an actual inspection of the situation of these 
mountains, of their elevation, and their form, of their base, and 
the proportion they bear to those surrounding them, would have 
been more to the purpose than any conjectures that might be 
hazarded upon the subject. Not knowing, however, when I 
might have opportunity or time to survey them in person, I can- 
not at present undertake to give a more detailed account of their 
extent." 
He then concludes with some speculations as to the origin of 
the phosphoric acid contained in the mineral, which it seems un- 
necessary here to repeat. 
The second memoir in the same work relative to this stone is 
by Don Christiano Heergen, but being confined to an account 
of the external characters belonging to the mineral, it neither 
corrects nor confirms the preceding statement regarding its extent 
and geological relations. 
Such then, so far as we have been able to ascertain, was the 
amount of information to be derived from Spanish authorities, 
that gave rise to those statements respecting this mineral which 
have excited so much wonder and interest; and even at Madrid 
so little was known as to the real nature of the formation in which 
it occurs, that the first authority there, the head of the mining 
department, and himself a very able man, informed us that it 
constituted a vein ("filon") in granite. 
Hence all that we could learn respecting the rock in question 
was only calculated, from its very vagueness, to stimulate our 
curiosity, and to excite our imagination as to its real nature, and 
thus to create in us a mutual desire to visit in person a spot 
remarkable for the })resence of so curious a substance. 
And as it was intimated to us, that several leading members of 
the Royal English Agricultural Society entertained a wish to 
learn how far the site of the mineral in question might be here- 
after reckoned upon for furnishing our fields with j)liosphate of 
lime, should other sources of its supply fall off, we flattered our- 
