132 Mr, J. Croll on the Physical Cause of the 



climate. " It seems to have become," says Sir Charles Lyell, 

 u a more and more received opinion that the coal-plants do not, 

 on the whole, indicate a climate resembling that now enjoyed in 

 the equatorial zone. Tree-ferns range as far south as the 

 southern parts of New Zealand, and Araucarian pines occur in 

 Norfolk Island. A great preponderance of ferns and lyco- 

 podiums indicates moisture, equability of temperature, and 

 freedom from frost, rather than intense heat"*. 



Mr. Robert Brown considers that the rapid and great growth 

 of many of the coal-plants showed that they grew in swamps 

 and shallow water of equable and genial temperature. 



" Generally speaking," says Mr. Page, " we find them resem- 

 bling equisetums, marsh-grasses, reeds, club-mosses, tree-ferns, 

 and coniferous trees; and these in existing nature attain their 

 maximum development in warm, temperate, and subtropical, 

 rather than in equatorial regions. The Wellingtonias of Cali- 

 fornia and the pines of Norfolk Island are more gigantic than the 

 largest coniferous tree yet discovered in the coal-measures "f* 



The coal-period was not only characterized by a great pre- 

 ponderance over the present in the quantity of ferns growing, 

 but also in the number of different species. Our island pos- 

 sesses only about 50 species, while no fewer than 140 species 

 have been enumerated as having inhabited those few isolated 

 places in England over which the coal has been worked. And 

 Humboldt has shown that it is not in the hot, but in the 

 mountainous, humid, and shady parts of the equatorial regions 

 that the family of ferns produces the greatest number of species. 



"Dr. Hooker thinks that a climate warmer than ours now is 

 would probably be indicated by the presence of an increased 

 number of flowering plants, which would doubtless have been 

 fossilized with the ferns ; whilst a lower temperature, equal to the 

 mean of the seasons now prevailing, would assimilate our climate 

 to that of such cooler countries as are characterized by a 

 disproportionate amount of ferns "J. 



The enormous quantity of the carboniferous flora shows also 

 that the climate under which it grew could not have been of a 

 tropical character, or it must have been decomposed by the heat. 

 Peat, so abundant in temperate regions, is not to be found in 

 the tropics. 



The condition most favourable to the preservation of vegetable 

 remains, at least under the form of peat, is a cool, moist, and 

 equable climate, such as prevails in the Falkland Islands at the 

 present day. " In these islands," says Mr. Darwin, " almost 



* Elementary Geolog)', p. 399. 



+ The Past and Present Life of the Globe, p. 102. 



X Memoirs of the Geological Survey, vol. ii. part 2. p. 404. 



