with Geographic Botany, — Temperature. 179 



other, and sweeping around them so as to expose their coasts 

 to its humid atmosphere and winds. We can hardly con- 

 template this arrangement without acknowledging a particular 

 object was to be obtained. Perhaps on this account it is that 

 it has always required rather a fanciful imagination to discover 

 that the continents and mountain ranges pursued a direction, 

 having a general connexion with the cardinal points. The 

 influence of the surface of the ocean will depend on the pre- 

 vious temperature ; thus in low latitudes, where the tempera- 

 ture is great, the former is constantly active in depressing it. 

 Sea-water rarely attains upwards of 86°, and the atmosphere 

 over it 88° ; as this latter is surpassed over the land, its de- 

 pression at sea is solely attributable to the equalizing power 

 of the surface of the ocean. The air also during the night 

 undergoes very small changes of temperature; and should 

 there be any disposition to a considerable fall, the surface of 

 the water is always ready, as a compensating agent, to part 

 with its heat to the coohng atmosphere. On this account the 

 island-climates of these parallels are not subject to such high 

 mean or daily temperatures as continents, and the range is 

 less extensive. The agreeable influence it has is sufficiently 

 prominent, and continues the same as we traverse higher lati- 

 tudes ; but its power of cooling the air gradually disappears, 

 till it entirely ceases between the twenty-fifth and thirty-fifth 

 degree, the exact spot fluctuating with the season of the year. 

 An opposite effect now commences; the ocean, instead of 

 cooling, parts with heat and elevates the temperature, whilst 

 its power of curtailing the range remains the same. Island- 

 climates have now higher annual and daily means, and are 

 equally preferable as protecting us from the disagreeableness 

 of another excess. 



The conditions of an island-climate of this kind are visible 

 over a very large portion of the continent of Europe, where 

 its peculiarities are often developed. A comparison between 

 its productions, and similar parallels on the continents of Asia 

 and America, will soon satisfy us as to this circumstance. In 

 Europe where the oak, ash, beech, and elm thrive, there are 

 in America gloomy forests of fir and cypress. At Nootka 

 Sound, in the western or warmer coast of America, and in a 

 lower latitude than London, a dense forest invests the surface, 

 consisting of species of Abies, Cupressus, Betula, and Cerasus, 

 with shrubs oiRibes, Rubus, Rosa, Vaccinium, and Andromeda, 

 Barley and rye are cultivated in Europe within the arctic 

 circle, and forests of Pinus sylvestris reach to the extremity 

 of the continent. Nothing like this occurs in America, where 

 we find instead a scanty vegetation of lowly bushes of Salix, 



