Phosphorite in Estremadura. 
415 
proportion varying from 15 to 20 per cent. ; but neither manganese nor 
any other new substance could be discovered in it. 
The quartzous veins, which alternate with the phosphorite, especially 
near the sides of the deposit, though consisting principally of silica, 
nevertheless contain iron, and a trace of phosphate of lime. 
Other small seams of phosphorite proceed to some distance obliquely 
out of this, the main deposit, into the clay-slate rock ; but none consist- 
ing of this mineral, unconnected with the one already mentioned, could 
we hear of, either in the neighbourhood of Logrosan, or in any other 
locality. 
From the spot crossing the road above mentioned we traced the de- 
posit in a S.S.W. direction across an olive plantation, down a gentle 
declivity, until we finally lost sight of it in the low ground beyond, 
about a mile from the road. Of course the phosphorite w as only visible 
at intervals through the covering of soil ; but the occurrence here and 
there of blocks or fragments of the mineral, and the conformity between 
the direction in which they appeared, and that of the previously observed 
portions of it, left no doubt in our minds as to this point. 
The phosphorite throughout its whole extent is extremely indestruc- 
tible, resisting the influence of the atmosphere, as well as of all the 
other agents of decomposition to which its loose fragments had been 
subjected. 
In none of those which we saw, whether on the tops of walls, or par- 
tially buried under the earth, however long they may have been exposed 
to the weather, was the slightest change discoverable. 
We were therefore anxious to ascertain, whether any influence had 
been exerted upon the suitableness of the soil for agricultural purposes 
by the presence in it of this mineral. 
The soil itself bore the character o'' a loam, according to the definition 
given in the Table on the Classification of Soils, published by one of the 
authors of this memoir, in Vol. 3, Fart 1, of the Journal of the Royal 
English Agricultural Society. 
1000 grains were separated by a mechanical analysis, conducted ac- 
cording to Mr. Rham's method, into — 
Grains. 
1. Coarse pebbles . . . . . 375 
2. Minute do. . . . . . .88 
3. Coarse powder ..... 388 
4. Impalpable powder passing through the finest 
sieve ....... 140 
Loss being ...... 9 
1000 
Of the latter 100 grains were examined, and found to consist nearly 
as follows : — 
Of Water 5 0 
Vegetable matter . . . . .45 
Sand 50-0 
Clay much charged with peroxide of iron . 40*0 
Carbonate of lime there seemed to be merely a trace. 
