44 FLORIDA REEFS. 
the slope of a high mountain in the Tropics, from base to summit, presents 
in a condensed form, an epitome, as it were, of the same kind of gradation 
in vegetable growth that may be observed from the Tropics to the Arctics. 
At the base of such a mountain we have all the luxuriance of growth 
characteristic of the tropical forest, — the palms, the bananas, the bread- 
trees, the mimosas; higher up, these give way to a different kind of growth, 
corresponding to our oaks, chestnuts, maples, &c. ; as these wane, on 
the loftier slopes comes in the pine forest, fading gradually, as it ascends, 
into a dwarfish growth of the same kind ; and this at last gives way to the 
low creeping mosses and lichens of the greater heights, till even these find 
a foothold no longer, and the summit of the mountain is clothed in per- 
petual snow and ice. What have we here but the sanie series of changes 
through which we pass, if, travelling northward from the Tropics, we leave 
palms and pomegranates and bananas behind, where the live-oaks and 
cypresses, the orange-trees and myrtles of the warmer temperate zone 
come in, and these die out as we reach the oaks, chestnuts, maples, elms, 
nut-trees, beeches, and birches of the colder temperate zone, these again 
waning as we enter the pine forests of the Ai'ctic borders, till, passing out 
of these, nothing but a dwarf vegetation, a carpet of moss and lichen, fit 
food for the reindeer and the Esquimaux, greets us, and beyond that lies 
the region of the snow and ice fields, impenetrable to all but the daring 
arctic voyager ? 
I have thus far spoken of the changes in the vegetable growth alone 
as influenced by altitude and latitude, but the same is equally true of 
animals. Every zone of the earth's surface has its own animals, suited to 
the conditions under which they are meant to live ; and, with the exception 
of those that accompany man in all his pilgrimages, and are subject to the 
same modifying influences by which he adapts his home and himself to all 
climates, animals are absolutely bound by the laws of their nature within 
the range assigned to them. Nor is this the case only on land, where 
river-banks, lake-shores, and mountain-ranges might be supposed to form 
the impassable boundaries that keep animals within certain limits ; but the 
ocean, as well as the land, has its faunae and florid bound within their 
respective zoological and botanical provinces; and a wall of granite is not 
more impassable to a marine animal than that ocean-line, fluid, and flowing, 
and ever-changing though it be, on which is written for him, " Hitherto 
shalt thou come, but no fiirther." One word as to the effect of pressure 
on animals will explain this. 
