AGE OP COAL. 235 



Where the flexures are most decided the strata were met- 

 amorphosed gneiss, granite, and other crystalline rocks 

 being produced showing that great heat was present at 

 that time in such localities. The same changes took place 

 in the coal-measures of other countries. The movements 

 in the bending and folding of the strata were not con- 

 fused, but occurred in certain lines, according to some 

 systematic plan of the Creator. They were probably 

 very slow perhaps to the extent of some yards, or even 

 feet only, in a century else such bendings without frac- 

 tures as are often found could not have been produced. 

 It is believed that, besides the metamorphosis of strata 

 which laid up at that time for the use of man such quan- 

 tities of building material, there were separated and de- 

 posited in this metamorphic process many of the precious 

 and other metals, and also many of the precious gems. It 

 has also been observed that the coal is most debitumin- 

 ized where the disturbances of the strata were the great- 

 est. This is probably to be attributed to two causes 

 the action of great heat in such localities, and the oppor- 

 tunity of escape for gaseous products given by the frac- 

 tures made in the disturbances. Denudation is often 

 connected with the faults, bendings, etc. This is exem- 

 plified in Fig. 68, p. 140. These denudations were some- 

 times vast, the thickness of strata removed amounting 

 even to many thousands of feet. 



338. Palaeozoic Life-record. You have now been 

 made acquainted to some extent with the changes in life 

 which occurred in the three Palaeozoic ages the Siluri- 

 an, Devonian, and Carboniferous. While the grand di- 

 visions marked out by the Creator are preserved from 

 the beginning, showing that the same general plan exist- 

 ed from the outset as now, the predominant forms of 

 life, especially of animal life, are very diiferent from each 

 other in the different ages, and very different from those 

 which appear at the present time. All the four divisions 

 of animals began in the first of the Paleozoic ages, the 



