FOREIGN CORRESPONDENCE. 



347 



carbonate of magnesia, which crystallizes in rhomboid laminse of a 

 pearly lustre. 



The cavities of the Eoman masonry contain Hyalite and other varieties 

 of Oped. Arragonite is also found in these cavities ; the samples are 

 bipyramidal crystals, very acute, resembling those found in the iron- 

 beds of Framont and certain basalt formations. Calcareous-spar is seen 

 mixed with the crystals of Chabasite before mentioned, and in the same 

 cavities are observed small crystals of Fluor-spar, which have, in some 

 places, their usual and beautiful violet tints. "We must add that 

 Professor Nickles, of N'ancy, has very recently discovered fluorine in 

 the mineral waters of Plombieres. Does the presence of this fluorine 

 (contained in the water in shape of fluorides) explain that of Daubree's 

 crystals of fluor-spar, or do the latter account for the discovery made by 

 Kickles ? There can be hardly any doubt that it is the presence of 

 certain fluorides in the waters of Plombieres that has given rise to the 

 formation of the Blue-John or fluor-spar seen by M. Daubree,* by their 

 action upon the lime of the Roman cement. 



In certain cavities and fissures where the Eoman cement is exposed 

 to a direct stream of warm water, a gelatinous substance is precipitated, 

 which, by contact with the air, hardens, becomes quite opaque, and as 

 white as snow. This substance analysed by M. Daubree, turns out to 

 be a new mineral, a silicate of lime, to which he attributes the 

 composition 



CaO Si 0^ + 2 HO 

 Silicate of lime + water. 



He calls it Plomlierite. 



In spite of the extreme hardness of the Eoman masonry, it gives, 

 nevertheless, access to the mineral water, which not only penetrates it 

 in all directions, but actually passes through it. This passage is very 

 slow, but continuous, and permits the chemical reactions which take 

 place to multiply slowly for an immense space of time — an experimental 

 element which modern chemists are in the habit of neglecting, but 

 which the old alchy mists knew well how to take into consideration.! 

 That time plays an important part in those essays by which we en- 

 deavour to imitate natural productions, is seen by those beautiful 

 experiments of M. Daubree's, to which we have before referred, and in 



* M. Jutier has just discovered at Plombi&res a large vein of Fluor-spar in the 

 granite, which is traversed by the mineral waters, and whence doubtless these 

 waters derive their soluble fluorides, which coming in contact with the lime of the 

 masonry are transformed anew into fluor-spar. — T. L. P. 



t Hortulanus, in the sixteenth century, says that to procure the Philosopher's 

 Stone, " On fait digerer pendant douze jours des suer de mercuriale, de pourpier," 

 &c- The celebrated alchymist Geber says, " I have seen mines of copper from 

 which particles of this metal were carried away by a current of water. This 

 water having dried up, the atoms of copper remained three years in the dry 

 sand. I discovered that at the end of this time they had been cooked and digested 

 by the heat of the sun and changed into laminss of pure gold. By imitating nature 

 we produce the same transformation." Hoefier, in his " History of Chemistry," 

 say that experiments begun by certain alchymists of the middle ages were often 

 transmitted from father to son as an inheritance ; and that the son, not having 

 lived long enough to terminate them, left them by will to his children. — T. L. P. 



2 D 2 



