INTRODUCTION. 



§ I. The primary object of " The Wind and Current Charts," 

 out of which has grown this Treatise on the Physical Geography 

 of the Sea, was to collect the experience of every navigator as to 

 the winds and currents of the ocean, to discuss his observations 

 upon them, and then to present the world with the results on 

 charts for the improvement of commerce and navigation. 



II. Accordingly, when this object was made known, and an ap- 

 peal was addressed to mariners, there was a flight up into the gar- 

 rets, and a ransackmg of time-honored sea-chests in all the mari- 

 time communities of the country for old log-books and sea journals. 



III. It was supposed that the records therein contained as to 

 winds and weather, the sea and its currents, would afford the in- 

 formation requisite for such an undertaking. 



lY. By putting down on a chart the tracks of many vessels on 

 the same voyage, but at different times, in different years, and 

 during all seasons, and by projecting along each track the winds 

 and currents daily encountered, it was plain that navigators here- 

 after, by consulting this chart, would have for their guide the re- 

 sults of the combined experience of all whose tracks were thus 

 pointed out. 



V. Perhaps it might be the first voyage of a young navigator to 

 the given port, when his own personal experience of the winds to 

 be expected, the currents to be encountered by the way, would it- 

 self be blank. If so, there would be the wind and current chart. 

 It would spread out before him the tracks of a thousand vessels 

 that had preceded him on the same voyage, wherever it might be. 

 and that, too, at the same season of the year. Such a chart, it 

 was held, would show him not only the tracks of the vessels, but 

 the experience also of each master as to the winds and currents by 

 the way, the temperature of the ocean, and the variation of the 



