48 
DEPOSITS OF PHOSPHATE OF LIME. 
[BULL. 
There are no signs of organic remains in the Nassau phosphorites, 
but they are generally believed to be of animal origin. Dr. Mohr 
thinks they were formed by the concentration of the phosphate of lime 
from the underlying limestones. At present not much phosphorite is ex- 
ported on account of the difficulty of freeing it from the associated iron 
and the expense of mining it. Several years ago, however, large quanti- 
ties were sent to England, and in 1867 the total output of all the mines 
amounted to 30,000 tons, which sold, according to its quality, for $5 to 
$8 per ton. It is still used in considerable quantities along the Rhine. 
Table of analyses of Nassau phosphorites. 
Lime 
Magnesia 
Sesquioxide of iron. 
Alumina 
Potash 
Soda 
Phosphoric acid 
Carbonic acid 
Silicic acid 
Fluorine 
Water 
Sulphuric acid 
Deduction for oxygen . 
Fresenius 
and Foster. 
Pure staf- 
felite. 
45.79 
0.16 
6.42 
1.08 
0.58 
0.42 
34.48 
1.51 
4.83 
3.45 
2.45 
Fresenius. 
101. 17 
1.45 
General 
sample. 
47.31 
0.12 
3.77 
1.67 
0.66 
0.52 
33.84 
2.75 
5.04 
2.11 
2,74 
100. 53 
0.84 
99.69 
Wicke. 
General 
sample. 
42.31 
0.23 
8.22 
2.23 
1.26 
0.09 
30.63 
2.78 
6.61 
3.74 
3.00 
1.07 
102. 17 
1.57 
100. 60 
PHOSPHORITES OF SOUTHWESTERN FRANCE. 
The phosphorites of the southwest of France are in the departments 
of Lot, Tarn-et-Garonne, and Aveyron. The region is limited by the 
valleys of the rivers Lere, Oelle, and Aveyron, and the phosphorite is 
found in largest quantities near Caylus and at St. Antonin, Limogne, 
Cajarc, Figeac, Villeneuve, Bozouls, and other places on the southwest- 
ern side of the central plateau. The material occurs in fissures and 
cavities in the surfaces of hard, compact, gray limestone plateaus which 
belong to the Oxfordo-Coralline group of the Jurassic formation. The 
deposits are of two kinds. 1 The first occurs in irregular cavities, never 
over a few yards long, and partaking more or less of the character of 
pockets ; the second, in the form of elongated leads, with sides which 
are nearly vertical and which run in a generally parallel direction, 
widening and narrowing at intervals. They are generally shallow and 
'Mr. Daubrec: Comptesreudus Acad.sci., Paris, vol. 73, 1871. 
(522) 
