SECONDARY ROCKS. 



87 



Coniferae .... 10 species. 

 Indeterminate . . 50 " 



- — 300 species. 



These facts seem to show conclusively that the 

 flora of the epoch of the coal formations was very 

 different from that of the present day, as the vegeta- 

 ble families which are now the most numerous 

 were then wholly wanting, and those which are 

 flow comparatively rare were then numerous. Ve- 

 getables also, which are now mere herbs, then at- 

 tained the size of large trees ; as, for example, the 

 ferns, which, though they now attain the height of 

 but a few feet at the most, then grew as large as 

 our tallest trees. This, among other facts, has 

 led geologists to believe that the climate of the 

 surface of the earth at that period was excessively 

 hot, and, not only so, but uniform in every latitude, 

 as the fossil remains of the coal formations of ev- 

 ery latitude are the same. But, at the present 

 time, every latitude, and, indeed, every different de- 

 gree of elevation, has its own species of plants. 



It is a remarkable circumstance also, that marine 

 remains -have rarely been detected in coal-beds, 

 although they abound in carboniferous limestone, 

 which lies below the coal measures ; which circum- 

 stance, if it does not prove the deposite of coal to 

 have been effected in fresh water, yet shows that 

 there was something which prevented the presence 

 of marine animals. De la Beche states that the 

 Yorkshire coal-beds in England contain the remains 

 of ammonites and pectines, and that the fossils of the 

 carboniferous limestone and coal measures are de- 

 tected in the millstone grit ; in other words, that 

 there was an alternation of terrestrial with marine 

 remains. The same fact has lately been noticed in 

 Germany. 



This accumulation of vegetable matter, at a re- 

 mote period in the history of the world, for the use 



