FORMS INDUCED BY CERTAIN LIMITS. 



83 



(75.) Geographical limits of the Sheep. — Every plant 

 and animal has certain geograpiiical limits, out of which 

 it cannot exist. With the exception of man and the 

 dog, no animal has a wider range than the sheep, ex- 

 tending- as it does from Iceland almost to the equator, 

 and from a few degrees south of that to the polar ex- 

 tremity of South America. But though existing under 

 •o great a variety of exposures, it must not be inferred 

 that it can come to perfection in them all. On the 

 contrary, it rather delights in the temperate zones, and 

 can evidently only be raised to its highest point of ex- 

 cellence in the countries of the vine. The western 

 parts of continents produce better sheep than the east- 

 ern, and the southern hemisphere better than the 

 northern ; as in the former situations the temperature 

 is more nearly equable than in the latter. The same 

 may be said of maritime districts, as compared with 

 such as are inland. Temperature is affected in the 

 same way by elevation as by northern or southern posi- 

 tion — the mean heat diminishing in the same ratio 

 when ascending a mountain, as in receding from the 

 equator. On this account, Humboldt compared the 

 earth to two mountains with their bases at the equator, 

 and their summits at the poles. The mean tempera- 

 ture, when resulting from the height of the place above 

 the level of the sea, is at the same time influenced by 

 the nature of the aspect, as we notice in the Alps, 

 where the Glacier exists on the northern side, at the 

 same elevation at which the vineyard yields a perfect 

 fruit upon the southern, 



(76.) Particular forms induced by certain limits,-^ 

 The character which a predominance of heat, or cold. 



