272 EXPERIMENTS ON METAMORPHISM AND 



epigeny between the gypsum and the sulphur. We may remark, 

 however, that the first phenomenon appears to be almost always ac- 

 companied by a high temperature, while the reduction of sulphates, 

 even in a state of solution, appears paralyzed by every elevation of 

 temperature capable of stopping the putrid fermentation or the de- 

 composition which organic matter spontaneously undergoes.* 



Bitumens and other carburets of hydrogen, according as they 

 are in a solid, liquid, or gaseous state, sometimes impregnate beds, 

 sometimes flow from them, (petroleum,) sometimes escape from the soil, 

 as in the salses, mud volcanoes, and inflammable springs, which are 

 in general only the vents of bituminous deposits, t The different 

 formations of bitumen present as general, or at least, remarkably 

 frequent characteristics: 



1. Of being associated with salt bearing formations, (Soultz-sous- 

 Forets in the Bas-Rhin, Landes; salt mines of Teklenbourg, in the 

 north of Germany; decrepitating salts of Wieliczka and other parts 

 of the Carpathian mountains, Brassa, near Spalatro; in Dalmatia, 

 Albania, Persia, China, United States, &c.) 



2. Of being situated in the neighborhood of combustible deposits 

 or formations containing beds of vegetable remains, (Lobsann, Basses- 

 Alps; Seefeld and Hering, in Tyrol: Bovey, in Devonshire; Derby- 

 shire, environs of New Castle and of Glasgow, &c.) 



3. Of being connected with accidents of igneous origin, both 

 ancient and modern; that is to say, volcanoes or eruptive rocks, (Yal 

 de Noto, near Etna; Auvergne; Gaujac, in the Landes, where bitu- 

 men flows, at the foot of a peak of ophite, from a saliferous forma- 

 tion containing lignite; Java, Cape Verd,) or of being associated with 

 dislocated formations, (Hering, in the Tyrol, salses of the Crimea, 

 and of the promontory of Taman| and of the Caspian sea, which are 

 in the prolongation of Caucasus.) 



4. Of being often accompanied by sulphurous hot springs and de- 

 posits of sulphur, (permian formation of the Volga, promontory of 

 Kertch, and various localities near the Caucasus, environs of Mosul, 

 in Persia.) These two last circumstances seem to result from the 

 associations of which we have spoken above. 



Several of my experiments account for these relations. By sub- 

 mitting pieces of wood to the action of superheated water I have 

 transformed them, in the midst of the water itself, into lignite, coal, 

 or anthracite according to the temperature, and have moreover ob- 

 tained liquid and volatile products resembling natural bitumens, and 



*The reduction of a sulphate to a sulphuret, according to the experiments of De 

 Senarmont, does not take place at high temperatures. Thus the conditions that are favor- 

 able to putrid fermentation are also suitable for the reduction of sulphates to sulphurets. 



I will add besides that the sulphuret of copper is formed and cr)'stallizes in the hot 

 springs of Plombiercs, at a temperature of about 70° centigrade, as I have elsewhere an- 

 nounced. — (Annales des Mines, 5th series, vol. xii , p. 294.) This phenomenon of reduction 

 explains perhaps, the origin of some beds of metallic sulphurets, such as the copper 

 bearing schists of Mansfield. 



f This last relation is apparent in the Appenines, in Albania, in the promontory of 

 faman, and in the environs of Tiflis, &c. 



^Mimoires de la Soci6t6 Giolo-jique de France, vol. iii, 1838. 



