102 Sir A. Crichton on the [Feb. 



there is no resemblance between the Floras of the two extreme 

 points. At the time, however, of the coal formation, the Flora 

 of these two remote parallels was the sapae, both as to genera 

 and species. 



If it be allowed that a variety in climate and soil are the two 

 chief circumstances which occasion the greatest variety in the 

 vegetable kingdom ; and if it be allowed that the plants of the 

 coal formation and of the most ancient strata were all of the 

 simplest structure, and almost entirely belonging to the acoty- 

 ledonous and monocotyledonous tribes, we have another proof 

 of the uniformity of temperature and soil at that period over an 

 immense extent of the earth. The more complicated vegetables, 

 those of the dicotyledonous kind, do not appear until a much 

 later period,* when the cause of the uniformity of temperature 

 of the ancient world was gradually becoming less and less, and 

 dying away, and the sun beginning to take an ascendency over 

 a cause of heat which had until then exerted supreme influence, 

 and which appears to have belonged solely to the earth itself. 



Whatever the temperature may have been which was neces- 

 sary to support the life of the vegetable kingdom of that early 

 period of the earth's existence, it miist be admitted that that 

 temperature was the same towards the polar regions as in the 

 tropical ones, for in both, the genera and species of antediluvian 

 plants are similar, and the shells and corals of the mountain 

 limestone in the most distant parts of the contemporaneous 

 strata also correspond with each other. In the collection of the 

 Geological Society of London, there is a specimen of a very 

 remarkable variety of felicites from the coal formation of Aus- 

 tralia, about the 29° south of the equator, and another exactly 

 resembling it from the coal formation of Newfoundland in the 

 49° north of the equator. The fossil shells of Van Dieman's 

 Land correspond with those of Derbyshire. Upon descending 

 below the coal formation, proofs of the equality of a high tem- 

 perature over the whole earth are multiplied ; for upon examin- 

 ing the mountain, and more especially the transition limestone, 

 which comes more immediately in contact with the primitive 

 rocks, we find madrepores, encrinites, corallites, and all the 

 varied habitation of sea polyps, the existing analogues of which 

 are always found in tropical climates. It is in the Pacific Ocean, 

 and chiefly in the Red Sea, the Persian Gulph, and the Carribean 

 Sea, that the greatest coral rocks of modern times are found. 

 But in the ancient world, not only pentacrinites, madrepores, 

 corallites, and encrinites, are found in the transition and moun- 

 tain limestone of the coldest regions, but also whole genera of 

 testacea, the living resemblances to which, with a few excep- 

 tions, are only to be met with at present in warm climates. 



si/' 



* In tlie Whitby coal which lies over the oolite. 



