114 DEPOSITS OF PHOSPHATE OF LIME. [BULL.4fi. 
When the nodules are cemented together in slabs, the masses are 
generally 1 to 2 feet square and 8 to 12 inches thick. Their upper sur- 
face is smooth, shiny, and mammillated ; the lower one, which is irregu- 
lar and uneven, shows plainly that the slabs are composed of nodules 
held together by a siliceous and calcareous cement. 
According to Yermoloff the beds of Smolensk, Orel, Kursk, and Wo- 
ronesch contain not less than 6,000 tons»per acre, while those of Tam- 
bov, which are said to be the richest in Russia, contain 20,000 to 30,000 
tons per acre. 
As regards the origin of these phosphates, Count Keyserling thinks 
that they were formed by carbonated waters dissolving the phosphate of 
lime of the bones and other phosphatic matter of dead animals and re- 
depositing it in a bed of siliceous and calcareous marl. 
The existence of ssamorod in central Russia has been known ever 
since the early part of this century, but its value was not appreciated. 
In the geological survey of Russia, by Sir R. Murchison, the phosphate 
rock is simply spoken of as u a shelly agglomerate and concretionary 
iron-stone," and several deposits of it are spoken of as " ferruginous, 
siliceous, and concretionary banks." The discovery that ssamorod is 
a phosphatic rock is due to Professor Chodneff, of St. Petersburg, in 
1845. Count A. Keyserling and Professor Claus, of Dorpat, first made 
known the existence of phosphate in the departments of Kursk and 
Woronesch a few years later. In 18GG, Professor Engelhardt, in his 
geological survey of Russia, afforded valuable information concerning 
the extent, value, and accessibility of the phosphatic beds. 
Several factories have been started to make use of these deposits, but 
generally with little success. Large works were started at Ukolowa, 
Riga, and in Kursk, but were soon closed. The phosphate is of too 
low grade to pay for the expense of mining it. 
Besides the beds already described, phosphatic deposits of much more 
limited extent have been found elsewhere in Russia. Thus Professor 
Schwackhofer, 1 of Vienna, has discovered a deposit of phosphatic nod- 
ules in the Silurian schists of Poland, on the Dniester. The average 
of tweuty-five analyses gave 74.23 per cent, bone phosphate, which 
is much higher than the average of Russian Cretaceous phosphates. 
The amount of phosphatic material in the bed is, however, very limited, 
and consequently it is of no commercial importance. A phosphatic 
limestone containing 12 per cent, of phosphoric acid had also been dis- 
covered in the government of Novgorod. 2 
1 Ueberdas Vorkomuien und die Bildung von Phosphoriten an den Ufern des Dnies- 
ter in Russisch-Podolien, Galizien und der Bukowina, by Professor Schwackhofer. 
2 A. Yermoloff, Jour, agric. pratique, vol. 1, 1872. 
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