50 RELICS FROM THE WRECK 



plants and trees. By a lately invented process, this exam- 

 ination is carried on with great accuracy. The coal is 

 sliced into thin leaves, and placed under a powerful glass. 

 In this way the peculiar character of the stem under exam- 

 ination is at once recognised, and the fact established that 

 the coal is of vegetable origin. An obvious inference is 

 drawn from this fact. The growth of these plants and trees 

 required time ; and the produce of many generations was re- 

 quired to make up even a thin bed of coal, the collecting 

 and consolidating, therefore, of only one bed, must have 

 stretched over a long period. It may be granted that vege- 

 tation, during the epoch of the earth's history of which we 

 are now treating, was more rapid and luxuriant ; Still our 

 conclusion is not affected much thereby. 



Some limestones are known to be composed almost en- 

 tirely of organic remains. The exuvice, of creatures, all too 

 minute to be detected by the unaided eye, are collected in 

 such masses as to furnish beds of rock many feet thick t 

 It is superfluous to say, that the formation of such rocks 

 must have been the work of time. Again, it is well known 

 that corals enter largely into the composition of limestone. 

 In some instances, it would appear that the rock is one mass 

 of these zoophytes. Now, from all we have been able to 

 learn of the habits and modes of operation of these diminu- 

 tive laborers, we are left to conclude, that the general progress 

 of the mass of calcareous matter which they secrete, is 

 slow. It has been calculated that the growth of six inches 

 requires a century.* Let the thickness of the beds, and the 

 number that occur in the earth's crust, be taken into account, 

 and we again find ourselves driven backward into an un- 

 known antiquity. 



In connexion with this argument, there is still another 

 point to which reference should, in justice, be made. The 

 fossils that exist in a given formation, are not identical with 



Williams' Missionary Enterprise in the South Sea Islands, p. 9. 



