22 2 YORKSHIRE NATURALISTS AT SALTBURN. 



found. The ruins of the alum works and the heaps of calcined 

 debris at Kettleness, as at Boulby, Loftus, and other places on 

 the coast, ail speak of the total extinction of an industry which had 

 existed in this district since the days of Queen Elizabeth. Thus for 

 centuries the alum shales of the Lias had been the only source 

 whence alum was produced, and it was only when the enterprise of 

 modern chemists discovered that from coal shales, and by utilising 

 the ammoniacal liquor from gasworks, that much speedier and 

 cheaper results were obtained, that this monopoly perished. 

 Naturally, the long use of the shales of the zone of A. communis^ as 

 above, has gready altered the contour and the colouring of the cliffs 

 in many places, for the refuse thrown over has made terraces and 

 mounds with a reddish hue. In an exposure of the shale at this 

 point Mr. Chadwick discovered a fine piece of fossilised wood, 

 showing in section the structure very plainly. Descending, the 

 harder shales of the zone of A. serpentimis followed, also the 

 compact bituminous rock, running in bands, or found in cheese- 

 shaped masses, between which the beautiful and familiar mineral 

 known as jet is found ; these beds receive from this cause the name 

 of jet rock. A good opportunity was here offered of observing the 

 stratification and the circumstances under which jet is discovered, 

 as a heading was being driven into the cliff about 8 feet high and 

 about 5 feet broad at the entrance, but much larger inside, and the 

 worker most laboriously hewing away, and industriously searching 

 for jet. One of the nodules was broken, showing the interior to 

 have been filled with bitumen, since hardened into jet, and radiating 

 in numerous cracks or crevices irregularly from the centre. The 

 shales of this zone are not only very bituminous, but are also strongly 

 charged with iron pyrites ; thus, when exposed to the air, as in the 

 cliffs, they will spontaneously ignite, and sometimes burn for years. 

 At different points on the coast, high up in the cliffs at inaccessible 

 elevations of two or three hundred feet, hugh red patches of calcined 

 shales were seen, resulting from these natural fires. Then succeeded 

 the grey shales of the zone of Ammonites annulatiis^ which, on the 

 present occasion, did not reveal any fossils, although in the balls of 

 argillaceous limestone, which occur here and there, may be found the 

 ammonite which gives its name to the zone. At the base of the 

 cliff the beds constituting the main seam of the ironstone series or 

 zone of Ammonites spinatus were noticed. Mr. Chadwick also 

 reported having seen on the beach a large travelled boulder of Shap 

 Fell granite, about 3 feet 6 inches in diameter. The party now 

 skirted the picturesque bay of Runswick, guarded by low cliffs of 

 boulder clay, the latter filling up an ancient valley of preglacial 



Naturalist, 



