51 



siderable elevation above the sea, and which are so 

 densely clothed with wood as to be scarcely penetrable, 

 almost destitute of insect life. Around such altitudes 

 however the clouds perpetually cling, and the rain is 

 well nigh incessant; and it would seem as if the very 

 dampness which causes the vegetation (especially the 

 ferns) to flourish in such rank luxuriance, and the timber 

 to rot with such rapidity that the gigantic trunks are 

 washed, reeking with moisture, down the mountain- 

 slopes, was too extreme for animal existence. 



Now, it wdll be remembered that the Madeiran group 

 is situated at a corresponding distance from the Equator 

 as Morocco, Algeria, the lower limits of Syria, Texas, 

 and Upper Florida are, all of which literally teem with 

 life; and that Tierra del Fuego lies between the same 

 parallels of south latitude as Durham and Central Russia 

 do in the northern hemisphere. From which it is 

 evident, that the equal removal of countries from the 

 earth's greatest heat does not necessarily imply an 

 equal exuberance in their Faunas, seeing that in both 

 the regions just appealed to, we not only perceive a vast 

 difference in the numbers of the insects which they re- 

 spectively contain, from those in other districts which 

 have a similar divergence from the tropics ; but we are 

 even able to recognize a certain resemblance of physical 

 conditions (and, therefore, of the creatures which have 

 been either adapted to, or modified by, them) in lands 

 so far asunder, not merely with respect to latitude, but 

 longitude also, as Madeira and Tierra del Fuego. 



