'l-GS Intelligence and Miscellaneous Articles. 



The author states, that a phenomenon which he observed in the de- 

 partment of Aveyron, gave him an opportunity of describing the na- 

 tural formation of an acid so much employed in the arts, and which 

 placed him in a condition in the localities which he has examined, of 

 readily manufacturing sulphuric acid, without having recourse to the 

 complicated processes generally employed. 



In the coal-measures of Aveyron, and particularly in the environs 

 of Cransac (arrondissement de Villefranche), the spontaneous com- 

 bustion of the soil is observed to occur, v/hich is evidenced by the 

 disengagement of gas and vapours, which at a distance resemble 

 a small volcano. On approaching the place where this combustion 

 occurs, it is evident that the earth has been mined, and large crevices 

 are discovered from time to time, from which there is emitted much 

 aqueous vapour and acid fumes. At the edges of these fissures the 

 heat becomes intolerable, and surprise ceases to be excited that the 

 effects of this heat, combined with the action of acid gases, should 

 have modified so completely the places in which these chemical ac- 

 tions occur. 



In some spots of the burning mountain, there occur enormous 

 rocks formed of conglomerates, which, having undergone the action 

 of fire, are completely changed in appearance, and are united by a 

 censent, which owing to the action of heat has a brick-red colour. 



The surface of the burning mountain consisted of grits, schists and 

 argills; these substances have assumed the appearance of chalcedonies, 

 jaspers, enamels, glass and bricks, and sometimes even the cavernous 

 appearance of volcanic stones. The aggregations which these sub- 

 stances have formed with argill have in some cases acquired the 

 hardness of the most compact stones. The soil, gradually mined 

 by the chemical agency occurring within it, eventually sinks, occa- 

 sioning the formation of foundries, which, by their conical form, re- 

 semble in some degree the craters of volcanos ; it is through these 

 vents that columns of vapour are disengaged, which sometimes rise 

 to a great height in the air, and are at other times dispersed by the 

 wind in the valleys. 



In these places a number of saline concretions, efflorescences, cry- 

 stals of sulphur and hydrochlorate of ammonia are met with ; these 

 products have been converted to useful purposes, and dissolved in 

 rain-water, they constitute the mineral waters frequently employed 

 in the locality now described. 



The causes of the phsenomena become evident to any one who has 

 ascertained the presence of sulphuret of iron, which occurs abun- 

 dantly in the various strata of coal country which constitute this 

 locality. 



This sulphuret, in contact with water and with atmospheric air, 

 burns and gives rise to sulphurous acid gas, which is converted into 

 sulphuric acid by the influence of air and of bases, such as alumina 

 and oxide of iron. The sulphates of iron and alumina which form 

 under these circumstances are decomposed by the action of heat, and 

 sulphuric acid is set free. 



The temperature resulting from these diflferent reactions is some- 



