ERA OF THE OLD RED SANDSTONE. 



37 



limited ; for instance, the Red Sea gives different polypi- 

 aria, zoophytes, and shell-fish, from the Mediterranean. 

 It is the opinion of M. Brogniart, that the uniformity 

 which existed in the primeval times can only be attribu- 

 ted to the temperature arising from the internal heat, 

 which had yet as he supposes, been sufficiently great to 

 overpower the ordinary meteorological influences, and 

 spread a tropical clime all over the globe. 



ERA OF THE OLD RED SANDSTONE — 

 FISHES ABUNDANT. 



We advance to a new chapter in this marvellous histo- 

 ry — the era of the Old Red Sandstone System. This term 

 has been recently applied to a series of strata of enormous 

 thickness in the whole mass, largely developed in Here- 

 fordshire, Shropshire, Worcestershire, and South Wales ; 

 also in the counties of Fife, Forfar, Moray, Cromarty, 

 and Caithness ; and in Russia and North America, if not 

 in many other parts of the world. The particular strata 

 forming the system are somewhat different in different 

 countries ; but there is a general character to the extent 

 of these being a mixture of flagstones, marly rocks, and 

 sandstones, usually of a laminous structure, with conglo- 

 merates. There is also a schist showing the presence of 

 bitumen ; a remarkable new ingredient, since it is a vege- 

 table production. In the conglomerates, of great extent 

 and thickness, which form, in at least one district the 

 basis or leading feature of the system, inclosing water- 

 w r orn fragments of quartz and other rocks, we have evi- 

 dence of the seas of that period having been subjected to 

 a violent and long-continued agitation, probably from vol- 

 canic causes. The upper members of the series bear the 

 appearance of having been deposited in comparatively 

 tranquil seas. The English specimens of this system 

 show a remarkable freedom from those disturbances 

 which result in the interjection of trap ; and they are thus 

 defective in mineral ores. In some parts of England the 

 old*red sandstone system has been stated at 10,000 feet in 

 thickness. 



In this era, the forms of life which existed in the Silu- 

 rian are continued : we have the same orders of marine 



