246 



YORKSHIRE ALUM WORKS. 



Aluminous 

 schist us. 



Volcanoes. 



and a sulphate of alumine is produced. The stratum is of 

 great extent, and inestimable value. I am not permitted to 

 point out its situation. 



The aluminous schistus is generally found disposed in ho- 

 rizontal laminse. Sometimes it exists in the form and ap- 

 pearance of indurated clay ; in fact the whole of the upper 

 part of the stratum resembles indurated clay, when first 

 wrought; but by exposure to the atmosphere it suffers de- 

 composition, and crumbles into thin layers. The upper 

 part of the rock is the most abundant in sulphur, and the 

 deeper they work into it, the quantity of sulphur decreases, 

 and the bituminous substance increases, and the rock be- 

 comes more hard and slaty ; so that a cubic yard of rock, 

 taken from the top of the stratum, is as valuable as 5 cubic 

 yards taken at the depth of 100 feet. 



When a quantity of the schistus is laid in a. heap, mois- 

 tened with sea water, it will take fire spontaneously, and 

 will continue to burn until the whole of the combustible 

 materials are exhausted. 



A considerable part of the cliff some years ago fell down 

 in a situation where it was exposed to the sea at high water; 

 in a short time afterward combustion had taken place 

 throughout the whole extent of this small volcano, and it 

 continued to burn for two or three years before it became 

 extinct. Does not this fact explain the nature and cause of 

 volcanoes ? This point I am aware has been ably ill ustrated 

 in the spontaneous inflammation of pyrites, the artificial 

 volcano of Lemery, and more particularly by the indefati- 

 gable Spallanzaiii, and Sir W. Hamilton. 



The whole extent of the aluminous strata bears evident 

 marks of a volcanic nature. It is intersected by whin 

 d} kes, and wherever the coal strata come in contact with 

 these dykes, the coal is charred to some distance. Wood is 

 also found in every part of the schistus converted into char- 

 coal. Jet appears to be some vegetable substance, that has 

 been acted upon by considerable pressure, and some degree 

 of heat, not sufficient to convei't it into charcoal; it fre- 

 quently has the appearance of a cylinder having undergone 

 ar) immense pressure, and the centre filled with pyrites. 

 The accumulation of sulphur towards the top of the strata, 

 as if it bad been sublimed — these lacts teem to countenance 



the 



