THE SEASON WHY. 313 



" He hth made the earth by his power, he hath established the world by hu 

 wisdom, and hath stretched out the heavens by his discretion." JBBEHIAH x. 



Eastern Asia, on the bants of the Argoun and the Amour; and the apple occun 

 again in the Aleutian Isles. 

 1237. The following are the northern limits of several trees in Scandir-aviaj 



Lat. 



Beech, Farjus silvatica ... 60 deg. niu. 

 . Hard Oak ,Quercvs robur 61 



Common Elm, Ulmtis campestria . 61 



Common Lime, Tilia communis *. 61 



Common Ash, Fraxinus excelsior . 62 



Fruit trees 63 



Hazel, Corylus avellana ... 64 



Spruce Fir, Abies excelsa ... 67 



Service Tree, Sorbus aucuparia . 70 



Scotch Fir, Finns silvestris . . 70 

 White Birch, Eetula alba . . 70 



Dwarf Birch, Setula nana . . 71 



12S8. Tnus distinct vegetable regions are observed on passing from south to 

 north through different climatic zones, defined as to their limits by the 

 Isothermal curves, and not by the parallels of latitude. Similar changes of vege- 

 tation mark a perpendicular transit through varying climates. A succession of 

 plants appear on the tropical mountains which rise above the snow line, corres- 

 ponding to those which are encountered iu mean and high latitudes. The 

 higher we ascend, the more does the number of the phsenogamic class diminish 

 in proportion to the cryptogamic, till only members of the latter family are 

 found, whose further progress upward is arrested by the everlasting snow. The 

 last lichen met with by Saussure on Mont Blanc, Silene acaulis, was also 

 observed by M. Brevais in the neighbourhood of Bosekop, lat. 69 deg. 58 min. 

 where it was vegetating on the sea-shore, shaded by the last pines of Europe. 



1239. Isolated mountains display to the best advantage the effect of climatic 

 change of vegetation. 



1240. Etna is divided into three great regions : La Regions Culta, or fertile re- 

 gion ; La Regione Sylvosa, or woody region ; La Regions Deserta, the bare or 

 desert region. But each of these is susceptible of sub-divisions, defined by the 

 presence of certain families of plants, forming seven botanical zones. 



1. The sub-tropical zone, which does not rise more than 100 feet above the 

 evel of the sea, is characterised by the palm, banana, Indian fig, sugar-cane, 

 varities of mimosa and acacia, which with us are only found in conservatories. 



2. The hffiy zone rises about 2,000 feet, characterised by the orange, lemon, 

 shaddock, maize, cotton, and grape plants. 



3. The woody zone lies between the height of 2,000 and 4,000 feet, where the 

 cork-tree flourishes, several kinds of oak, the maple, and enormous chesnuts. 



4. The zone between the height of 4,000 and 6,000 feet is distinguished by the 

 beech, Scotch fir, birch, and, among small plants, by clover, sandwort, ttt* 

 weed, dock, and plantain. 



K The sub-alpine zone, between the elevation of 6,000 and 7,500 feet, producw 

 the barberry, soap-wort, toad-flax, and juniper. 



6. The zone between 7,500 and 9,000 feet, has almost all the plant* of the p*- 

 ceding, with the fleshy and jagged (ptMttB. 

 14 



