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hot springs of Bourbonne-les-Bains. Finally, Vivianite has 
been observed in the products of the coal pits of Commentry, 
when under combustion, where it appears to be the result of an 
alteration of rhabdite (phosphure de fer météorique.) Vivianite 
has been obtained by Becqurren by bringing gently into com- 
munication two solutions that were suitable, by their mutual 
re-action, to generate this mineral. The operation was made 
ina V formed tube, one of whose branches contained a solution 
of sulphate of copper, accompanied by a plate of copper, to 
maintain it in a saturated state, and of which the other branch 
of the tube enclosed a solution of phosphate of soda, with a 
thin plate of iron immersed. Between these two liquids a 
layer of clay was interposed, whereupon a phosphate of copper 
was produced, which the iron decomposed slowly, and in measure 
of its production, and on the surface of the iron plate a 
group of crystals was developed, which had the composition of 
Vivianite, and, like it, assumed a blue colour on contact with 
the air. 
M. Davsree has also obtained in the laboratory of the 
College of France, in 1861, some delicate crystals of Vivianite, 
similar to those of Commentry, by subjecting to feeble varia- 
tions of temperature the amorphous precipitate which is 
produced by bringing into contact two solutions, one of sulphate 
of iron and the other phosphate of soda, the latter salt being 
in excess. 
To ForcnuHammer is due the artificial re-production of a 
crystallized phosphate of iron which only differs from Vivianite 
in being anhydrous. This substance is obtained by melting 
together a mixture of sulphate of iron, phosphate of soda, and 
chloride of sodium ;—after washing and decanting the residuum 
which is formed, a crystalline powdered substance is left, whose 
composition is represented by the formula: 38 FeO, PhO’, and 
which assumes on exposure to the air the bluish colours of the 
natural mineral Vivianite. 
The application of the foregoing results to Geology is this— 
Vivianite appears to be re-produced in nature after the manner 
of secondary minerals, by a double decompositicn. This natural 
