576 



SCIENTIFIC RECREATIONS. 



marine worms, encrinites, molluscs, and other zoophytes in great variety. 

 We find also a number of graptolites, trilobites, echinus (sea-urchin), 

 terebratula, and many other forms. 



The Trilobites were amongst the first creatures inhabiting our globe, 



and it is a curious fact to 

 contemplate, that their eyes 

 (fig. 655) should have been 

 preserved perfect ; they pre- 

 sent one of those wonderful 

 objects which carry one's 



Fig. 6 S3 .-Triiobite. thoughts backwards to the 



early ages of the world, probably many millions of years, 

 and yet it is found by the peculiar structure of the eyes of 

 these Trilobites that they were placed at the bottom of the Fig - 654> ' 

 sea with perfect power to look upwards at the light of the sun through the 

 transparent waters. The same hand and the same power had then Divine care 

 and solicitude for the well-being of His creatures, as great as He has for those 

 of later ages, and these animals are mentioned in Genesis " Let the waters 



bring forth abundantly the moving creature 

 that hath life." 



Thus we see that ages of comparative 

 quiet succeeded the first great contraction of 

 the earth's crust, probably millions of years, 

 during which time the tides and currents of 

 the ocean had to wash and wear down all 

 the thousands of projecting rocks or in- 

 equalities, and dissolve (as before described) all the lime, depositing the sand 

 and clay in those immense strata which form the old-named " transition 

 series " ; this appears to have taken place over nearly the whole world at 

 that time, and ages upon ages must have elapsed to form such deposits 

 as the sandstone, claystone, and 

 limestone, in alternation, forming the 

 " Llandilo," " Caradoc," and " Wen- 

 lock" strata, more than a mile in 

 thickness ; these are by some geolo- 

 gists reckoned among the primary 

 series (by some called the " transi- 

 tion rocks "), and in England form 

 the " Cambrian " and " Silurian" sys- 

 tems which are so rich in minerals 

 and metallic veins. 



The OLD RED SANDSTONE, or 



DEVONIAN System, is the next Of the F 'S- 656.-Limestone made up of encrinite. 



series of layers which built up our earth, but a great gap of years separates 

 it from the Silurian. We find the " Old Red " in the Mendips and in 



Fig. 655. Eye of Trilobite. 



