170 THE OLD COAL-MEASURES. 



cay, and how few are necessarily washed down into estuaries 

 and seas of deposit, it is wonderful to learn that such fra- 

 gile remains as those of insects, land-shells, and tree reptiles 

 should have been saved from destruction. And surely, if 

 larger and stronger forms had existed, the hope may be in- 

 dulged that they too have been preserved, and will one 

 day or other be detected. 



Such is a hurried glance at the Life of the old Carbonifer- 

 ous period, and more especially as displayed in the areas of 

 Europe and North America, where mining operations have 

 been most extensively conducted. Whether these extensive 

 coal-fields were all contemporaneous is a subject open to 

 question. Indeed, the probability is that they were not 

 strictly contemporaneous, but merely belonged to a great 

 cycle of the earth's history characterised by these coal- 

 forming conditions, and in the main by the sanies facies of 

 plants and animals. But however this may be decided by 

 future and more exact inquiry, we perceive in the mean 

 time a wonderful similarity all over the old coal-measures, 

 and an exuberance of life that has never been excelled dur- 

 ing any subsequent epoch. To account for this exuberance, 

 especially in the vegetable world, various hypotheses have 

 been advanced, such as a greater proportion of carbonic 

 acid in the atmosphere, the greater amount of heat derived 

 in those earlier times from the interior of the globe, a 

 general lowering of the land-surfaces, and a higher temper- 

 ature over the coal-yielding areas arising from some change 

 (inclination of the earth's axis or otherwise) in the astrono- 

 mical relations of our planet. In the present state of our 

 knowledge and belief in the stability of the earth's planetary 

 relationships such hypotheses are inadmissible, and we are 

 driven to seek for the solution in the then distribution of 

 sea and land, the climate thereby produced, the nature of 



