CHAMBERS'S INFORMATION FOR THE PEOPLE. 



crawled and left their tracks ; gravelly beaches, 

 that have become conglomerates ; and great beds 

 of shells, that have given origin to thick lime- 

 stones. Life gradually assumes more activity, and 

 living forms become more numerous and elevated 

 in the scale of existence, as we ascend in the 

 system towards the active period that follows. 



IV. DEVONIAN AND OLD RED SANDSTONE 

 SYSTEM. 



Description. This system of rocks has been 

 rendered famous through the writings of several 

 geologists, especially the celebrated Hugh Miller, 

 and is one that in itself possesses the very greatest 

 interest. In early geology, the Coal-measures 

 were considered very important ; and as both 

 below and above them a great thickness of red 

 sandstone is found, the rocks above were named 

 the New Red Sandstone; while those below, being 

 of course older, were called the Old Red Sandstone, 

 or, shortly, the Old Red. This system consists of 

 two types, the Fresh-water or Old Red, and the 

 Marine or Devonian, so called from being exten- 

 sively developed in Devonshire. These two types 

 may not be of the same age, or if so, were de- 

 posited under different conditions. The Old Red 

 is largely developed in the centre and north of 

 Scotland, especially in Forfarshire and Caithness, 

 where it is extensively quarried, and in parts all 

 over the world. The name ' Old Red ' indicates 

 that the chief rock is a red sandstone, which is 

 used very extensively for building. This also 

 occurs in fine flags used for pavement, generally 

 of a gray colour, yielding the famous Arbroath 



and Caithness pavements. The remarkable rock 

 called Conglomerate or 'Plum-pudding Stone,' 

 which looks as if it consisted of a consolidated 

 sea-beach, is also extensively found at the base of 

 the system. Like strata abroad coincide more 

 with the Marine or Devonian than with the Old 

 Red. They are found in many parts of the world,, 

 and extensively with fine fossils in Russia and 

 North America. Both types are divided into 

 three groups Lower, Middle, and Upper. 



Organic Remains. There are fewer plant than 

 animal remains found in this system. We find, 

 sea-weeds of different kinds, marsh-plants like our 

 bulrushes, sedges and horse-tails, tree-ferns and 

 reeds, &c. Late discoveries have greatly increased 

 the number of plants, so long thought to be so- 

 meagre, to above 200, rendering this system 

 almost half as rich as the Coal-measures in this 

 respect. Animal remains are numerous, varied, 

 and beautiful. There are many species of corals 

 and shells. The tracks of certain creatures, and 

 deep burrows, sometimes eighteen inches deep 

 and one and a half across, made by large burrow- 

 ing worms, are frequently found. Many crusta- 

 ceans are obtained, one of which is a huge kind 

 of crab, sometimes six feet long, with terrible- 

 looking toothed claws, called the Pterygotus^ or 

 ear-wing. Reptiles are also found, two very large 

 lizards being most frequent. 



But by far the most numerous specimens of 

 ancient life are gigantic fishes. These creatures 

 are all covered with hard bony scales, burnished 

 with enamel, with fierce teeth, and great fins 

 armed with long sharp spines, with which they 

 defended themselves or attacked their enemies. 



Cephalaspis, 5 or Shield-head. 



Coccosteus, 8 or Berry-bone. 

 Old Red Sandstone Fishes. 



Pterichthys, 4 or Winged-fish. 



These fishes have received different names, ac- 

 cording to peculiarities in their structure or 

 appearance, and have been brilliantly described 

 by Hugh Miller, who, when cutting the Old Red 

 Sandstone as a mason, had his attention first 

 drawn to geology by the brilliancy of their scaly 

 armour. 



Scenery of Period. The wide oceans in which 

 the thin fine-grained flags were deposited must 

 have been smooth and tranquil. Round the coral 

 islands that rose in its gleaming waters coursed 

 huge fierce fishes. The sandy shores became the 



26 



coarser sandstone. Within tide-mark, numerous 

 great crabs lived, and caught their prey in their 

 toothed claws ; shrimp-like creatures danced over 

 the sands, and in them worms burrowed ; the 

 waves ebbed and flowed, leaving their ripple-marks 

 on the rocks we now see ; gravel beaches fringed 

 the shore, where the surges rounded the pebbles 

 and rolled the stones, helping to create our 



1 From Greek pteron, a wing, and ous, etos, the ear. 

 * From Greek cephale, the head, and aspis, a shield. 

 8 From Greek coccos, a berry, and osteon, a bone. 

 4 From Greek pteron, a. wing, and ichthys, a fish. 



