1826.] which appear on tJie Yorkshire Coast. 359 



their details in the diffs south of Whitby, and in the great alum 

 works at the Peak, Sandsend, Boulby, and Lofthouse. 2. A bed 

 about the same thickness as the preceding, more compact, and 

 in the lower portion containing more nodules and concretions. 

 Near the bottom, the calcareous matter is most abundant, and 

 the beds assume the precise appearance of the lias formation : 

 consisting of bands and flattened nodules of argillaceous lime- 

 stone alternating with seams of shale. Seme of these nodules 

 contain petroleum, and many when struck give out a strong bitu- 

 minous odour, which, however, differs from the hepatic odour so 

 commonly given out by fetid limestone. 3. Hard, almost com- 

 pact slate-clay, about 30 or 40 feet thick, which makes a smooth 

 water-worn cliff, and forms the base of the whole group. The 

 lower parts of this group may be studied with advantage in the 

 cliflP north of Robin Hood's Bay, and in the cliflfuear Runswick 

 Bay.* 



(2.) The next group is very well defined, and wherever 

 it appears, makes a prominent feature in the cliff. It is about 

 120 feet thick, and may be subdivided into the two following 

 portions. 1. Beds of shale, rather meagre and micaceous, alter- 

 nating with concretions and thin beds of clay ironstone. The 

 concretions of ironstone often contain much calcareous matter, 

 and put on the form of septaria. In the lower part of this set 

 of beds, they are least abundant, and only present themselves in 

 the form of a few scattered nodules. 2. Thin beds of micaceous 

 sandstone divided by seams of meagre micaceous slate-clay. 

 The sandstone is in some places siliceous ; in others calcareous 

 and shelly, and not unfrequently passes into a rough argillaceous 

 flag-stone. This portion, which is generally more thick and 

 prominent than the one which is superior to it, is well exposed 

 in the cliff north of Robin Hood's Bay, and in the cliff" near 

 Staiths. 



(3.) The lowest group exposed in the sections of Boulby and 

 Huntcliff, very much resembles the upper part of the first group. 

 It is, however, generally less smooth and laminated, and is 

 not so liable to decomposition. Some portions of this group 

 are sandy ; and it is also traversed by som^ beds of impure shell 

 limestone ; the whole thickness exposed in the sections on the 

 coast is above 100 feet. 



The united thickness of the exposed parts of these three 

 groups amounts, therefore, almost to 600 feet. And in some 

 fruitless attempts to find coal, nearly 300 feet of still lower beds 

 were formerly pierced through, without reaching the bottom of 



* The cliffs composed of the first group are often intersected by a double system of 

 fissures, which divide the shale into rlioniboidal masses. This fact is very common in 

 formations of grey wacke slate, and indeed in argillaceous deposits of every age. Small 

 (Crystals of selenice abound in some parts of the decomposing shale. In a vein which 

 intersected the cliff near Runswick Bay, I met with somecryistalsof seleniteofextraordi. 

 nary beauty. 



