192 Pi'of. Biscliof on the Inflammable Oases of 



clay, from which no vapours issued, but merely hot air at a 

 temperature of from 120° to 126° R. (302" to 315° F.) 



The second view of the subject, viz. that the oxidation of 

 the sulphur in the alum-slate was set agoing by the original 

 conflagration, and is still continued, is suppoi'ted by the facts, 

 that sulphur is still sublimed, and is found in beautiful crystals 

 on the sides of the fissiu-es ; and that the watery A-apours have 

 an acidulous, aluminous smell, like that emitted by alum-slate 

 furnaces, and redden litmus paper. 



The sal-ammoniac, which occurs as a sublimate in some of 

 the fissures, deserves particular attention. Its formation is 

 easily understood, when we take into account the nitrogen 

 contained in the coal ; but it is remarkable that, in the sal- 

 ammoniac fissures, no burning smell is perceptible, — a fact 

 which leads us to suppose the simultaneous evolution of in- 

 flammable gas. I wish to be understood to mean, that though 

 no actual conflagration takes place in the stratum, yet the 

 coals which occur at some distance from the former burning, 

 can be subjected to a distillation by means of the heat which 

 prevails in the whole rocky mass. Now, as ammoniacal salts 

 are produced in our gas-works, and are formed at the same 

 time as the other products of distillation ; so it might be ex- 

 pected that this should happen likev.ise in burning rocks. 

 But here the sal-ammoniac appears without the other products 

 of dry distillation ; and this is a proof that other relations must, 

 in this case, exist. 



In reference to the inflammation of the stratum, which is 

 said to have taken place 178 years ago, it is to be remarked, 

 that the whole coal tract of the valley of Suhbach, to the Ba- 

 varian frontier, is much less inclined to inflammation than the 

 portion lying further to the north. On the contrary, the coal 

 there is very rich in bitumen, and at the same time vei'y easily 

 ignited. But, on that account, it is particularly suited to eon- 

 version into coke. The alum -slate also there has no ten- 

 dency to spontaneous combustion. 



By combining the phenomena presented by the burning 

 mountain, with the previous views on the evolution of inflam ■ 

 mable gas, and on the formation of mineral-oil, I only wished 

 to shew, that periods enn occur in coal connagratioiis, in wliicli 



