HARDWICKE'S SCIENCE-GOSSIP. 



171 



neighbourhood of York has a breadth of over twenty 

 miles, but contracts considerably to the northward. 

 The lower member of this formation, the Bunter Sand- 

 stone, rises to a slight elevation above the general flat 

 of the valley and may be seen at several places along 

 its western margin, one of the best sections in the 

 rock as mentioned above being the railway cutting 

 near Cattal station on the York and Harrogate rail- 

 way. 



This concludes the list of rocks found in our 

 western district, the first formation that is seen on 

 the east of York being, as we have said, the Keuper 

 Marl, which is first exposed at about nine miles from 

 the city, the whole of the intervening space, a distance 

 of eighteen miles, being completely covered by super- 

 ficial deposits. 



The Keuper Marl is, like the other members of the 

 Trias, from its containing no fossils, not of particular 

 geological interest; it, however, contains thin beds of 

 sandstone which have on their surfaces pseudomor- 

 phous crystals of salt, showing that the rock was 

 formed near the edge of brackish water. The Keuper 

 Marl forms a series of low hills or ridges to the east of 

 Stamford Bridge, which are not much above the 

 general level of the valley, the first rising ground 

 being formed by the Rhaetic and Lias. The first of 

 these formations forms a narrow outcrop at the base 

 of the hills, but is usually much hidden by drift, so that 

 it is very rarely we get an exposure of the beds 

 except in the neighbourhood of Northallerton, where 

 the streams to the east of the town give some good 

 sections. The Lias throughout its range from Cleve- 

 land to the Humber forms a steep bank at the edge 

 of the great Triassic plain and separates it very dis- 

 tinctly from the ranges of hills formed by the Oolites 

 and the chalk. The three divisions into which the 

 Lias is separable are usually as well marked physically 

 as they are palreontologically ; the lower portion, 

 consisting principally of clay, with thin bands of 

 limestone, does not present any very striking features, 

 but forms low undulating hills, which are more or 

 less masked by drift ; the Middle Lias, consisting of 

 harder beds, such as sandstone and ironstone, forms 

 a well-marked feature or terrace above this, and is 

 succeeded by the soft shales of the Upper Lias, form- 

 ing a steep bank below the escarpment of the Oolite. 

 The lower portion of the Lias may be studied with 

 most_ advantage at Redcar, where extensive reefs of 

 these shales crowded with fossils are exposed at low 

 water ; they are also well seen in the pits which have 

 been dug for marling the sandy land at Cliff to the 

 south of Market Weighton. The Middle and Upper 

 Lias are best seen in the magnificent sections on the 

 coast at Peak, Robin Hood's Bay, Hawsker Bottoms, 

 Whitby, Staithes, and Boltby, all of which places are 

 well worthy of a visit from those in search of geology 

 or the picturesque. 



The Oolites in that part of their outcrop nearest to 

 York, the Howardian Hills, consist of three main 



divisions. Upper, Middle, and Lower, the two latter 

 of which are capable of subdivision into several 

 minor groups, having very distinct lithological 

 characters. 



The Lower Oolites consist in the main of a great 

 series of estuarine beds separated by thin, but well- 

 marked limestones, namely the Dogger, the Hydraulic 

 Limestone, the Millepore Bed, the Grey Limestone, 

 and the Cornbrash ; the latter of these, however, 

 has not been found in the Howardian Hills, appar- 

 ently having thinned out in this part of its course, 

 as also is the case with each of the other beds, which 

 disappear in some part of their extended outcrop 

 across the county. 



One of the most marked features in the geology 

 of north-east Yorkshire is the Trap Dyke, which, 

 starting from beyond Cockfield Fell in Durham, 

 crosses the Tees, and ranges thence by Stainton, 

 Great Ayton, along the valley of the Esk to the 

 Goathland and Fylingdales Moors, where it finally 

 disappears a short distance before reaching the 

 main branch of the Derwent. Its total length is 

 about sixty miles, but it does not reach the surface in 

 all parts of its course, and in the valley of the Tees 

 is hidden by vast accumulations of Drift. This great 

 subterranean wall of basalt has a thickness of about 

 sixty feet, but contracts somewhat towards its eastern 

 end. The rocks which it traverses are the Carboni- 

 ferous Limestone, Millstone Grit, and Coal Measures 

 in Durham, and the Trias, Lias, and Lower Oolite 

 in Yorkshire, and all of these are more or less baked 

 and altered in the vicinity of the dyke. 



The Middle Oolites consist of an alternating series 

 of thick sandstones, slate, and limestones, which are 

 frequently liable to pass into one another without 

 any very marked lines of division ; the names of the 

 several divisions and the order of succession of these 

 beds commencing from the bottom is Kellaway 

 Rock, Oxford Clay, Lower Calcareous Grit, Passage 

 Beds, Lower Limestone, Middle Calcareous Grit, 

 Upper Limestone, Upper Calcareous Grit, The 

 whole of these divisions are, however, not always 

 present ; thus, in the Howardian Hills there is only 

 one bed of Limestone above the Lower Calcareous 

 Grit, and farther south the whole of the Middle 

 Oolites is represented by a thin band of Calcareous 

 Grit or Kellaway Rock. The Kellaway Rock, apart 

 from the coast section, is best seen in the romantic 

 gorge to the north of Pickering, through which the 

 railway to Whitby runs ; it here forms a series of 

 natural cliffs on either side of the line between 

 Levisham and Goathland stations, forming one of the 

 grandest scenes in this part of the country. 



The Oxford Clay and Lower Calcareous Grit 

 constitute the northern edge of that great range to 

 which the name of the Tabular Hills has been given, 

 which, starting from the coast at Scarborough, 

 strikes across the country in a bold escarpment 

 facing the north to the Hambleton Hills above 



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