g94 GEOLOGY. 



teeth, with coprolites, their fossil excrement, are scattered through the limestone strata, 

 some of which were of great magnitude, and evidently voracious, from the formidable 

 weapons with which they are armed. 1. represents, a tooth belonging to the tribe 



of Hybodants, a family of sharks 

 analogous to the living genus, the Port 

 Jackson shark : and, 2. a tooth of the 

 Megalichthys, a gigantic sauroid fish, 

 from the limestone of Burdie-house 

 near Edinburgh. Mr. Murchison 

 found in Russia the scales of this 

 creature, which belongs to the car- 

 boniferous system, in an upper bed of the old red sandstone, mingled with those of the 

 Holoptychius, noticed in the last chapter, which belongs to the sandstone formation ; and 

 in the strata at Burdie-house, forming the lower part of the coal series, the scales of both 

 are intermingled. " Both ichthyolites cross, as it were, the borders of their respective 

 formations. The one witnessed the closing twilight of the more ancient system, the 

 other the dawn of the system which succeeded it. They were cotemporaries for a time, 

 somewhat in the manner that Shem was cotemporary with Isaac." 



Millstone Grit. The coarse sandstones which form the principal part of this deposit 

 are chiefly distinguished by their great induration ; and the evidence afforded of mecha- 

 nical formation from the detritus of pre-existing masses. Quartoze particles of various 

 sizes, with rounded particles of felspar occasionally, agglutinated by an argillaceous 

 cement, compose the grit, in which beds of shale are interspersed, and impure bituminous 

 limestone, with thin seams of coal of an inferior quality. It forms the surface of elevated 

 moorlands, covered with a vegetation of brown or purple heath, mosses, and groups of 

 pines, and in several instances the grit occurs as a kind of cap to insulated mountains of 

 shale. Kinder- Scout, the loftiest eminence in the Peak of Derbyshire, the subject of the 

 local adage, indicating the long reign of winter upon its brow, 



4 



" If there be snow without; it will lie on Kinderscout." 



is a huge mass of shale with a cap of millstone grit. It is extensively developed in 

 northern and central England, and forms an important component of the wild scenery in 

 the neighbourhood of Matlock, capping the High Tor at the entrance of the valley, and 

 composing the remarkably bold escarpment of Stonni, the strata at various points 

 exhibiting great disturbance, being split and shattered in every direction, and abruptly 

 projecting from the general mass in a highly inclined position. " I stood," says a tourist, 

 "on the top of Stonnis (Stone-house) huge masses of rock (millstone grit) lay scattered 

 at my feet a grove of pines waved their dark branches over my head. I have scaled 

 the highest eminences in the mountainous districts of Derbyshire seen from their sum- 

 mits the sweet dales that repose in tranquil beauty at their base marked the multitude 

 of hills included within the wide horizon they command ; but not an eminence that I 

 ever before ascended not a prospect, however rich and varied, which I thence descried 

 was at all comparable with the view from Stonnis." 



Marine shells occur in the millstone grit, and vegetable impressions in the shales,, analo- 

 gous to those which are so abundant in the superjacent strata, to which we proceed. 



Coal Measures. Alternations of layers of variable nature and thickness compose this 

 important formation, the chief of which consist of sandstone, shale, ironstone, and coal, 

 which gives its name to the entire series. The two latter may be styled new products in 

 the economy of the globe, for though iron exists in veins in the older rocks, and is diffused 

 through some of them as a colouring matter, layers of clay-ironstone first appear in the 



