THE GROWTH OF COAL 251 



has, throughout its long history, been continually depriving the 

 atmosphere of its carbon dioxide, and accumulating this in 

 beds of coal. In the earlier ages indeed, this would seem to 

 us to have been its main use. 



To the modern naturalist, vegetable life, with regard to its 

 uses, is the great accumulator of pabulum for the sustenance 

 of the higher forms of vital energy manifested in the animal. 

 In the Palaeozoic this consideration sinks in importance. In 

 the Coal period we know few land animals, and these not vege- 

 table feeders, with the exception of some insects, millipedes, 

 and snails. But the Carboniferous forests did not live in vain, 

 if their only use was to store up the light and heat of those 

 old summers in the form of coal, and to remove the excess of 

 carbonic acid from the atmosphere. In the Devonian period 

 even these utilities fail, for coal does not seem to have been 

 accumulated to any great extent, though the abundant petro- 

 leum of the Devonian is, no doubt, due to the agency of aquatic 

 vegetation. In addition to scorpions, a few insects are the 

 only known tenants of the Devonian land, and these are of 

 kinds whose larvae probably lived in water, and were not 

 dependent on land plants. We may have much yet to learn 

 of the animal life of the Devonian ; but for the present, the 

 great plan of vegetable nature goes beyond our measures of 

 utility ; and there remains only what is perhaps the most 

 wonderful and suggestive correlation of all, namely, that our 

 minds are able to trace in these perished organisms structures 

 similar to those of modern plants, and thus to reproduce in 

 imagination the forms and habits of growth of living things 

 which so long preceded us on the earth. 



In another way Huxley has put the utilitarian aspect of the 

 case so admirably, that I cannot refrain from quoting his clever 

 apotheosis of nature in connection with the production of coal. 



" Nature is never in a hurry, and seems to have had always 

 before her eyes the adage, * Keep a thing long enough, and 



