Page:Physical Geography of the Sea and its Meteorology.djvu/99

 Rh York amounted in value to two millions and a half; from Pennsylvania, to $3,820,000; and from Charleston alone, to $3,834,000. But in 1795—by which time the Gulf Stream began to be as well understood by navigators as it now is, and the average passages from Europe to the north were shortened nearly one-half, while those to the south remained about the same—the customs at Philadelphia alone amounted to $2,941,000, or more than one-half of those collected in all the states together.

190. The shortening of voyages.—Nor did the effect of the doctor's discovery end here. Before it was made, the Gulf Stream was altogether insidious in its effects. By it, vessels were often drifted many miles out of their course without knowing it; and in bad and cloudy weather, when many days would intervene from one observation to another, the set of the current, though really felt but for a few hours during the interval, could only be proportioned out equally among the whole number of days. Therefore navigators could have only very vague ideas either as to the strength or the actual limits of the Gulf Stream, until they were marked out to the Nantucket fishermen by the whales, or made known by Captain Folger to Dr. Franklin. The discovery, therefore, of its high temperature assured the navigator of the presence of a current of surprising velocity, and which, now turned to certain account, would hasten, as it had retarded, his voyage in a wonderful degree. Such, at the present day, is the degree of perfection to which nautical tables and instruments have been brought, that the navigator may now detect, and with great certainty, every current that thwarts his