These facts are dependent on the eastward set of this majestic current; and so is another great physical fact of immeasurable importance to us;--the superiority in temperature of the western shores of Europe over the eastern shores of North America. The harbour of St. John's, Newfoundland, is frequently fast closed by ice in the month of June; yet the latitude of St. John's is considerably south of that of the port of Brest, in France. Impelled by the rotatory motion of the earth, and by the trade-wind,[106] the equatorial waters of the Atlantic are ever urged, a broad and rapid river, into the Caribbean sea, and the Gulf of Mexico, the narrowing shores of which compress the stream as in a funnel. The Andes here present a slender but impregnable barrier to its further progress westward; and the trend of the Isthmus turns it to the northward. Still finding no outlet, the impatient current, like a wild-beast pacing round its cage, courses the Gulf of Mexico, doubles the peninsula of Florida, and pursues its way first to the north-east, and then to the east, crossing the Atlantic in a retrograde direction, until it laves with its warm billows the coasts of Europe. Here it turns to the southward, and after embracing the "Fortunate" isles that lie off the African shores,--the Azores, the Madeiras, and the Canaries,--it joins the great equatorial set beneath the trade-wind, and returns on its westward course. This mighty circulation of water must have been going on from the instant that the earth commenced rotating on its axis, or (granting this to have been chronologically subsequent) from the instant the Atlantic occupied its present bed. Whether sooner or later, it commenced at _some_ instant; but at that instant all the previous elements of the circle were presupposed, and a boundless succession of former circles. An intelligent stranger, looking on the movement immediately after its commencement, but ignorant of its origin, would not be able to assign any limit to its past duration. From his observation of the velocity of the current in different parts of the circle, he would say with confidence,--"These identical particles of water, which I see now urged on their ceaseless course towards the middle of the North Atlantic, were, yesterday morning at this hour, in the latitude of the mouth of the Chesapeake; on the morning before, off Cape Hatteras, on the morning before that, off Cape Lookout;" and so backwards interminably.