2 INTKODUCTION. 



The length of the coast-lines which bound the North Atlantic and its 

 chief bays (except the Mediterranean), measured around their principal 

 sinuosities, is not less than 62,000 miles ; if more minutely estimated, it 

 would amount to much more. A Table is given presently, showing the 

 figures which make up this sum. Of these coasts, about 7,000 miles, or 

 one-ninth, remain unsurveyed ; but they are the Arctic regions, unfre- 

 quented by commerce. Of the remainder, two-fifths have been surveyed 

 by the Englisk Government, and three-fifths by foreign powers. The 

 whole of the coasts of the Atlantic Ocean are now represented on our 

 charts with the most minute accuracy in nearly all places of interest to 

 the sailor. 



The first Chart of the Atlantic Ocean, upon a large scale, was published 

 in Amsterdam by the renowned but now extinct house of Van Keulen, in 

 the middle of the eighteenth century. It was issued under the title of 

 the Spanish or West Indian Sea, and contained some useful details, amidst 

 a thousand errors. The second, entitled a Chart of the Atlantic Ocean, 

 was engraved at London, on the circular projection, invented by Mr. Mur- 

 doch, but was found to be extremely inaccurate, and the constructor 

 added to the Cape Verdes, two islands, under the names of St, Philip 

 and St. John, neither of which existed ; these names being sometimes 

 given by the Portuguese to the Islands Fogo and Brava. 



The next, which was the first of the kind published in this country, was 

 constructed by M. de la Eochette, a painstaking and talented hydro- 

 grapher, in 1777 ; and was published by the house whence the present 

 work issues, in that year. It was drawn upon the basis of the observa- 

 tions of M. Fleurieu, and for many years was in large demand ; of which 

 some degree of proof was given by its having been during that period 

 repeatedly copied, and illegally published. In the course of time, many 

 improvements were obtained, and it was superseded, in 1812, by another 

 of the same scale and size, constructed by Mr. John Purdy, a name well 

 known to mariners for many years. This chart, in its various editions, 

 did good service to seamen for a long period. 



These charts in their turn, requiring many improvements, from the 

 great acquisition of exact knowledge during recent years, it was deemed 

 necessary to supersede them by the charts which have been published 

 by the proprietor of this work, as compiled from the now nearly perfect 

 geographical data. They moreover exhibit, at one view, a summary, in a 

 graphic form, of all that range of phenomena with which hydrography has 

 of late been enriched. 



But there is one drawback to the great increase of observation. Each 

 department of hydrography is overloaded for practical every-day use, and 

 the seaman would waste much time in endeavouring to elicit some system 

 from the multifarious authorities he has now before him. A system of 

 mean results has therefore been adopted, as will be hereafter explained, 

 under the various sections wiiich follow. 



Hydrography, as at present understood, commenced with Captain Cook, 

 in his celebrated first voyage to the South Seas, in 1768. Previous to this, 

 our coasts were represented and corrected by the rude draughts and im- 

 perfect reckonings of painstaking mariners, in the pursuit of their profes- 



