56 THYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY. 



of the Andes, contracting with the Isthmus of Darien, and 

 stretching themselves out over the plains of Central Amen'ca 

 and Mexico. Beginning on the summit of this range, we leave 

 the regions of perpetual snow, and descend first into the tierra 

 iemjplada, and then into the terra caliente, or burning laud. De- 

 scending still lower, avc reach both the level and tlie surface of 

 the Mexican seas, where, were it not for this beautiful and benign 

 system of aqueous circulation, the peculiar features of the 

 surrounding countr}^ assure us we should have the hottest, if not 

 most pestilential climate in the world. As the waters in these 

 two caldrons become heated, they are borne off by the Gulf 

 Stream, and are replaced by cooler currents through the Carib- 

 bean Sea ; the surface water, as it enters here, being 3° or 4°, 

 and that in depth even 40° cooler than when it escapes from the 

 Gulf.* Taking only this difference in surface temperature as an 

 index of the heat accumulated there, a simple calculation will 

 show that the quantity of heat daily carried off by the Gulf 

 Stream from those regions, and discharged over the Atlantic, is 

 sufficient to raise mountains of iron from zero to the melting- 

 point, and to keep in flow from them a molten stream of metal 

 greater in volume than the waters daily discharged from the 

 Mississippi Eiver. 



156. Its benign influences. — Who, therefore, can calculate the 

 benign influence of this wonderful current upon the climate 

 of the South ? In the pursuit of this subject, the mind is led 

 from nature up to the great Architect of nature ; and what mind 

 will not the stud}^ of this subject fill with profitable emotions ? 

 Unchanged and unchanging alone, of all created things, the 

 ocean is the great emblem of its everlasting Creator. "He 

 treadeth upon the waves of the sea," and is seen in the wonders 

 of the deep. Yea, " He calleth for its waters, and poureth them 

 out upon the face of the earth." In obedience to this call, the 

 aqueous portion of our planet preserves its beautiful system of 

 circulation. By it heat and warmth are dispensed to the extra- 

 tropical regions; clouds and rain are sent to refresh the dry 

 land ; and by it cooling streams are brought from Polar Seas to 

 temper the heat of the torrid zone. At the depth of two hundred 



* Temperature of the Caribbean Sea (from tlie journals of Mr. Dunsterville) : 

 Surface temperature: 83^, September; 84^, July; 83 ^-86^^, Mosquito Coast. 

 Temperature in depth : 48^,240 fathoms; 43^, 3SG fathoms; 42^, 450 fathoms; 

 43^, 500 fathoms. 



