386 GEOGRAPHICAL DISTRIBUTION OP ANIMALS. 



of Guyana, differ as widely from those of Lake Superior as 

 the palms differ from the pine forests. 



[ 637. But, however active these physical agents may be, 

 it would be very un philosophical to consider them as the 

 source or origin of the beings upon which they show so exten- 

 sive an influence. Mistaking the circumstantial relation under 

 which they appear for a causal connection, has done great 

 mischief in natural science, and led many to believe they un- 

 derstood the process of creation, because they could account 

 for some of the phenomena under observation. But, however 

 powerful may be the degree of the heat ; be the air ever so 

 dry, or ever so moist ; the light ever so moderate, or ever so 

 bright ; alternating ever so suddenly with darkness, or passing 

 gradually from one condition to the other ; these agents have 

 never been observed to produce anything new, or to call into 

 existence anything that did not exist before. Whether acting 

 isolated or jointly, they have never been known even to modify 

 to any great extent the living beings already existing, unless 

 under the guidance and influence of man, as we observe among 

 domesticated animals and cultivated plants. This latter fact 

 shows, indeed, that the influence of the mind over material 

 phenomena is far greater than that of physical forces, and thus 

 refers our thoughts again and again to a Supreme Intelligence 

 for a cause of all these phenomena, rather than to the so- 

 called natural agents. 



[ 638. The physical agents whose influence upon organized 

 beings we have just examined, show a regular progression in 

 their action, agreeing most remarkably with the degrees of 

 latitude on one side, and the elevation above the level of the 

 sea oh the other. Hence the difference in the vegetation, as 

 we proceed from tropical regions towards the poles, or as 

 we ascend from the level of the sea to any height along the 

 slopes of a mountain. In both these directions there is a 

 striking agreement in the crder of succession of the pheno- 

 mena, so much so, that the natural products of any given lati- 

 tude may be properly compared with those occurring at a 

 given height above the level of the sea ; for instance, the vege- 

 tation of regions near the polar circles, and that of high moun- 

 tains near the limits of perpetual snow under any latitude. The 

 height of this limit, however., varies, of course, with the lati- 

 tude. In Lapland, at 67 north latitude, it is three thousand 



