Those ocean traversers evidently belong to a system. Some are permanent, some are periodical, and some are casual. The permanent arise chiefly from the effect of the flow from the poles to the equator. Descending from the poles in the first instance, they pour north and south. They gradually feel the earth's rotation; but on their arrival at the tropics, being still inferior in velocity to the equatorial sea, they seem to roll backwards; in other words, they form a current from east to west. This current is farther impelled by the trade-winds.
The progress of this great perpetual current includes almost every part of the ocean. In going westward, it necessarily rushes against the coast of America, where it divides into two vast branches, one running south with great force, and the other north-west. A succession of currents, all connected, obviously form a "moving power" to prevent the stagnation of the ocean, and, by their branches, visit every shore of the globe.
Some of those currents are of great breadth, but they generally move slow. Humboldt calculates that a boat, carried only by the current from the Canaries to Caraccas, would take thirteen months for the voyage. Still there would be obvious advantages to navigation in moving along a district of ocean in which all the speed, such as it was, furthered the movement of the vessel, and which offered none of the common sources of hindrance.
But another curious effect of the Atlantic currents is to be commemorated, as giving us probably the first knowledge of the western world. "Two corpses, the features of which indicated a race of unknown men, were thrown on the coast of the Azores, towards the end of the fifteenth century. Nearly at the same period the brother-in-law of Columbus, Pedro Correa, governor of Porto Santo, found on the strand of the island pieces of bamboo of an extraordinary size, brought thither by the western currents."
Those coincidences might have confirmed the idea of the great navigator. But Columbus still deserves all the glory. A thousand conjectures may be formed, and a thousand confirmations given, and yet all be lost to the world. The true discoverer is the man of practice. Columbus was that man; and we are to remember also his indefatigable labour in realising that practice, the unexhausted resolution with which he struggled against the penury and neglect of the Continental courts, his noble scorn of the sneers of European ignorance, and the heroic patience with which he sustained the murmuring of his crews, and asked "but one day more." The world has never seen a man more equal to his great purpose; if he was not a direct instrument appointed to the noblest discovery of man.
But those evidences of connexion are not unfrequently given to our more observant time. "When the wind has been long from the west, a branch of the Gulf Stream runs with considerable force in a north-easterly direction towards the coasts of Europe. By this the fruit of trees belonging to the torrid zone of America is annually cast ashore on the western coasts of Ireland and Norway. Pennant observes, that the seeds of plants which grow in Jamaica, Cuba, and the adjacent countries, are collected on the shores of the Hebrides. Thither also barrels of French wine, the remains of vessels wrecked in the West Indian seas, have been carried. In 1809, H.M.S. Little Belt was dismasted at Halifax, Nova Scotia, and her bowsprit was found, eighteen months after, in the Basque Roads. The mainmast of the Tilbury, burned off Hispaniola, in the Seven Years' War, was brought to our shores.
"To the Gulf Stream, England and Ireland are partially indebted for the mildness of their climate. The prevailing winds are the south-west. Coming over a vast space of the comparatively heated ocean, it is calculated, that if those winds were so constant as to bring us all the heat which they are capable of conveying, they would raise the column of air over Great Britain and France, in winter, at once to the temperature of summer."
But interesting as it might be thus to range through the great phenomena of the globe, and demonstrate its abundant and astonishing adaptation to the purposes of living existence, our more immediate object is to mark to the reader the materials of this noble volume.
The especial sciences of which it treats are, geology, hydrography, meteorology, and natural history, with their several subdivisions; the whole delivered in the most intelligible form of modern knowledge, and with the fullest information acquired by modern research; and illustrated by maps, the skill of whose execution can have been equalled only by the labour of their formation.
The volume commences with the geological structure of the globe in all its branches, and with separate articles given to the mountain chains of Asia, Africa, Europe, and America, all illustrated by maps: then follow the glaciers and glacial phenomena, with maps; then the phenomena of the volcanoes and volcanic regions, developed by charts and descriptions,—this department closing with that most curious, most disputed, and still most obscure of all subjects, the Palæontology of the British Isles.