the atmosphere, as it winds along the course of the stream. The latent heat of this vapour when it is set free produces a still greater rarefaction, so that we may imagine there is in the atmosphere a sort of cast of the Gulf Stream, in which the barometer often stands low, and into which, as into the equinoctial calm belt (§ 175), the wind often blows from both sides. In this fact is probably to be found an explanation of the phenomena alluded to above, viz.: that certain storms, both in the Atlantic and in the United States, invariably make for the Gulf Stream, and, reaching it, turn and follow it in its course sometimes entirely across the ocean. Hence, the interest that is attached to a proper series of observations on the meteorology of the Gulf Stream.
179. Storms of—dreaded by seamen.—Sailors dread its storms more than they do the storms in any other part of the ocean. It is not the fury of the storm alone that they dread, but it is the "ugly sea" which these storms raise. The current of the stream running in one direction, and the wind blowing in another, create a sea that is often frightful.
180. Routes formerly governed by the Gulf Stream.—The influence of the Stream upon commerce and navigation.—Formerly the Gulf Stream controlled commerce across the Atlantic by governing vessels in their routes through this ocean to a greater extent than it does now, and simply for the reason that ships are faster, nautical instruments better, and navigators are more skilful now than formerly they were.
181. Difficulties with early navigators.—Up to the close of the last century, the navigator guessed as much as he calculated the place of his ship; vessels from Europe to Boston frequently made New York, and thought the landfall by no means bad. Chronometers, now so accurate, were then an experiment. The Nautical Ephemeris itself was faulty, and gave tables which involved errors of thirty miles in the longitude. The instruments of navigation erred by degrees quite as much as they now do by minutes; for the rude "cross staff" and "back staff," the "sea-ring" and "mariner's bow," had not yet given place to the nicer sextant and circle of reflection of the present day. Instances are numerous of vessels navigating the Atlantic in those times being 6°, 8°, and even 10° of longitude out of their reckoning in as many days from port.
182. Finding longitude by the Gulf Stream.—Though navigators had been in the habit of crossing and recrossing the Gulf Stream
