of the Yorhhire Coast. 209 



The same bed contains numerous nodules of what we may call 

 cement stone, being the stone from which Roman cement is ma- 

 nufactured. The nodules vary in their form and size: they are 

 often globular, and sometimes two are joined by a slender bar, 

 so as to resemble a double shot. Many of them are coated with 

 a shell of pyrites, a quarter of an inch think, and of a bright me- 

 tallic lustre: thev often contain extraneous fossils. These stones 

 appear to be principally composed uf argillaceous and calcareous 

 earth, with oxide of iron, so mixed by nature as to form the pro- 

 per composition for terras, or Roman cement. 



On the top of the aluminous schistus rests a stratum of hard 

 compact stone, from six to twelve feet in thickness. The work- 

 men call it dogger, a name which they also give to the cement 

 stone ; and indeed its component parts seem to be nearly the 

 same, but with a greater mixture of iron. The colour of the recent 

 fracture is blueish gray, but, when exposed to the atmosphere, 

 it changes to a deep purple brown. The transverse partings di- 

 vide the stone into large blocks, nearly cubical ; each parting 

 contains thin plates, resembling rusted iron, and between the 

 plates a soft ferruginous earth, apparently the result of decompo- 

 sition. This bed of stone always covers the aluminous schistus 

 where the strata are entire. 



■ The superincumbent strata consist of alternate beds of indu- 

 rated clay, iron-stone, coal, bituminous shale, and granulated 

 sandstone; varving in number and thickness, according to the 

 height of the hills in which they occur. The indurated clay al- 

 ways rests on the dogger. It is of a light ochrey colour, is soft 

 and grittv, and divided into thin laminae. Alternating with the 

 strata of clay are several thin beds of iron-stone, and generally 

 one or more seams of coal. Where the surface is low, the coal is 

 i^eldom more than an inch or two in thickness; but where the 

 hills are highest, the principal seam is from six to eighteen inches. 



■ A little above the coal seam, there usually occurs a bed of sili- 

 ceous sandstone, 20, .'^0, or even 40 feet in thickness. Over this 

 stratum, bituminous shale and sandstone rise, in alternate beds, 

 to the tops of the hills, in the first three ranges formerly described. 

 Nodules of rich iron-stone abound in the shale: some of them 

 are of the granulated kind, in which the green specks that often 

 occur seem to indicate the presence of copper. 



In the upper end of Tripsdale, a branch of Bilsdale, is a bed 

 of l)ituminous schistus, of a dark brown colour, and soapy feel. 

 It is easily divided into tliin plates, which are used by the inha- 

 bitants of the neighbouring vales for baking cakes. The slates 

 are soft and clastic when first dug out ; but are prepared by roast- . 

 ing them in hot turf ashes, after which they will bear the heat of 

 a common fire for several years. 



Vol. 51. No. 2;JJ), M«/T/i 181S. ^0 Astra- 



