48 ERA OF THE CARBONIFEROUS FORM Al ION 



this era, and are only as yet found in isolated cases, and 

 in sandstone beds. The first discovered lay in the Craig- 

 leith quarry, near Edinburgh, and consisted of a stem 

 about two feet thick, and forty-seven feet in length. 

 Others have since been found, both in the same situation 

 and at Newcastle. Leaves and fruit being wanting, an 

 ingenious mode of detecting the nature, of these trees 

 was hit upon by Mr. Witham, of Lartington. Taking 

 thin polished cross slices of the stem, and subjecting them 

 to the microscope, he detected the structure of the wood 

 to be that of a cone-bearing tree, by the presence of cer- 

 tain " reticulations" which distinguish that family, in ad- 

 dition to the usual radiating and concentric lines. That 

 particular tree was concluded to be an araucaria, a species 

 now found in Norfolk Island, in the South Sea, and in a 

 few other remote situations. The coniferae of this era 

 form the dawn of dicotyledonous trees, of which they may 

 be said to be the simplest type, and to which, it has alrea- 

 dy been noticed, the lepidodendra are a link from the mo- 

 nocotyledons. The concentric rings of the Craigleith and 

 other coniferae of this era have been mentioned. It is 

 interesting to find in these a record of the changing sea- 

 sons of those early ages, when as yet there were no human 

 beings to observe time or tide. They are clearly traced ; 

 but it is observed that they are more slightly marked 

 than is the case with their family at the present day, as 

 if the changes of temperature had been within a narrower 

 range. 



Such was the vegetation of the carbonigenous era, com- 

 posed of forms at the bottom of the botanical scale, flow- 

 ^rless, fruitless, but luxuriant and abundant beyond what 

 the most favored spots on earth can now show. The ri- 

 gidity of the leaves of its plants, and the absence of fleshy 

 fruits and farinaceous seeds, unfitted it to afford nutriment 

 to animals ; and, monotonous in its forms, and destitute 

 of brilliant coloring, its sward probably\inenlivened by 

 any of the smaller flowering herbs, its shades uncheered 

 by the hum of insects, or the music of birds, it must have 

 bean but a sombre scene to a human visitant. But nei- 

 ther man nor any other animals were then in existence to 

 look for such uses or such beauties in this vegetation. It 

 was serving other and equally important ends, clearing 

 (probably) the atmosphere of matter noxious to animal 

 life, and storing up mineral masses which were in long 



