used for Agricultural Purposes. 
413 
when ground fine and treated with sulphuric acid produce light 
coloured concentrated superphosphates. They find a ready sale 
in the English market, and fetch a better price per unit per 
cent, of phosphate of lime than coprolites and mineral phos- 
phates containing much oxide of iron and alumina, inasmuch as 
superphosphates made from high grade Spanish phosphate retain 
their high percentage of soluble phosphate unaltered on keeping ; 
whilst those made from materials containing much oxide of 
iron and alumina, on keeping become poorer in soluble phos- 
phate, a portion of the soluble phosphate becoming precipitated, 
or reduced into insoluble phosphate by the presence of oxide 
of iron and alumina. 
7. Gekmax or Xassau Phosphate. 
In 18G4, Mr. Victor !Meyer of Limburg, subsequently pro- 
prietor of several extensive phosphate mines in the Duchy of 
Xassau, made the important discovery of a rich phosphate 
deposit in the neighbourhood of Staffel, a village near Limburg, 
in the Lahn Valley. 
This discovery created a good deal of sensation at the time, 
and gave a powerful stimulus to enterprising men to search 
the length and breadth of the Lahn \ alley and adjoining dis- 
tricts for phosphates. These explorations brought to lis'h': the 
existence of phosphate deposits in many other places in the 
Lahn Valley ; and at the present time phosphate mines are 
worked in the neighbourhood of Wetzlar, Weilburg, Lim- 
burg, Dehren, Staffel, Medingen, Weilbach, and numerous other 
places. 
The most extensive Lahn phosphate deposits are found on the 
left side of the River Lahn below Weilbach. The phosphate 
occurs in pockets, more particularly in places where limestone, 
dolomite, greenstone, and a siliceous rock, called, locally, Schal- 
stein, are intermixed with each other. It is found in these 
pockets embedded in a ferruginous clay, and is obtained in 
lumps of various sizes differing greatly in appearance. 
In some places the Nassau phosphate forms compact masses, 
having an earthy fracture, and light grey or yellow colour. In 
other localities it appears as a kind of conglomerate of broken 
pieces of phosphate cemented together by a red or brown- 
coloured clay, and intermixed with greenstone, manganese, and 
ironstone. More rarely it occurs in slates with a shaly fracture, 
and still more rarely in crystalline masses. 
Frequently it has a cellular and porous structure, and occurs 
