208 Geological and Mirier alog leal Sufvey 



60 feet in thickness, the colour changes to a light yellowish gray^ 

 and we find here some bands of iron-stone, alte'rnatina; with the 

 schistus. Below this part, the rock recovers its softness and 

 smoothness; and at the depth of 140 feet more, the schistus siuk^ 

 below tiie level of the sea, and how far it descends has not hither- 

 to heen ascertained. 



From the experinifnts made by Mr. Winter*, the schistus is 

 found to contain alumine, silex, magnesia, lime, oxide of iron, 

 bitumen, sulphur, and water; the proportions of which varycon-' 

 siderablv in different parts of the bed. The upper part abounds 

 most with sulphur, and therefore yields the greatest quantity of 

 ahim ; a cubic yard at the top being as valuable as five cubic yards 

 at the depth of 100 feet. Of course the specific gravity of the 

 schistus is not uniform : Mr. Winter states it at 2*4S. — Calc spar 

 often occurs in the veins of the rock. 



The aluminous schistus abounds with pyritc, which makes it 

 subject to spontaneous combustion, wheii great quantities of that 

 substance become suddenly exposed to moisture and the effect? 

 of the atmosphere. Some years ago, a considerable part of the 

 cliff between Sandsend and Kettleness fell down and took fire, 

 and continued to burn for two or three years. 



In this bed, that curious stone, called conical coralloid, occurs 

 in ai)undance. It is found adhering, like a shell or crust, to large 

 oval or lenticular blocks of hard calcareous stone, from which it 

 is not easily separated. It is composed of an immense number 

 of cones, from an inch to six inches in height, with all their api- 

 ces pointing towards the central block, and the interstices be- 

 tween them filled with calcareous matter. The cones are va- 

 riously aggregated; the larger containing several concentric 

 cones within them, and one cluster often encroaching on another, 

 or reclining on the side of another, so as almost to make their 

 apices meet. When the stone is broken, the cones are very 

 discernible in the fracture, and may often be taken out singly, or 

 in clusters : they are transversely marked with undulating striae, 

 and their structure appears lamellatcd. In colour and feel, the 

 stone resembles the alum-rock; but it properly belongs to the 

 calcareous tribe, and bears some analogy to the stink stone. — 

 The lenticular masses, incrusted by this fossil, are from a foot to 

 six feet in diameter. In some of them are cavities, lined with 

 crystals of calc spar, and filled with petroleum in a very fluid 

 state. From the fragments of these stones exudes a kind of pitch, 

 or indurated petroleum, which readily melts with heat, and when 

 icnited burns with a crackling noise, and emits a strong bitumi- 

 Iious smell. 



• See his Essay in Nicholsovi's PhilosophicalJownal, for April, 1810> 

 p. 247. 



The 



