520 THE POPULAR SCIENCE MONTHLY. 



on which the chart has been constructed, and an explanation of the 

 conventional signs used on it ; these latter, however, are generally- 

 supposed to be known. 



General notes regarding the winds, currents, tides, harbor facili- 

 ties, etc., are frequently added, as also sometimes sailing-directions ; 

 but generally these are left for text-books, which, under the titles of 

 " Directions," " Memoirs," " Manuals," or " Pilots," give to the navi- 

 gator the information obtained by the hydrographer, with the general 

 results arrived at, which cannot be engrossed on charts. 



By a judicious arrangement and a complete index, these should be 

 made as intelligible and as ready for reference as possible, and should 

 contain all the points within the area treated on that are of interest 

 to navigation. 



The first treatise on marine surveying, published in a practical 

 form, was by Alexander Dalrymple, in 1771. This was followed by 

 the work of M. Beautemps Beaupre, in 1808 ; since which time there 

 have been published many valuable works on marine surveying, 

 adapted both to running surveys and to greater geodetical operations. 



In hydrographic surveys and exploration, England has always been 

 foremost. Her Hydrographic Ofiice, dating from 1795, under Al- 

 exander Dalrymple, was not firmly established until 1828, when Cap- 

 tain Francis Beaufort became the hydrographer to the British Admi- 

 ralty ; since which time, under the administration of the line of dis- 

 tinguished navy officers his successors, it has steadily advanced, to 

 the inestimable benefit of commerce, both British and foreign. At the 

 present date the charts of this office number two thousand nine hun- 

 dred and eighteen, and yet about one-half of the coasts and navigable 

 waters of the world remain unsurveyed, a great part not even examined. 



An interesting skeleton chart of the world, compiled at the British 

 Hydrographic Office and attached to a paper delivered by Commander 

 Hull, R. N., superintendent of the Admiralty charts, before the Royal 

 United Service Institution, showed the portions of the coasts of the 

 world surveyed, partially surveyed, and only explored. Taking this 

 continent alone, between the parallels of 60 north and 60 south, be- 

 yond which whaling-vessels only generally go, it will be found by rough 

 measurement that about 12,000 miles of the seacoast have been sur- 

 veyed, 20,000 miles partially surveyed, and that 8,000 have been only 

 explored. Coasts partially surveyed or only explored require the 

 utmost caution for safe navigation ; and, even with this, vessels are 

 constantly in peril. For the remainder of the globe, with exception 

 of Europe, the proportion of the inadequately-surveyed and almost 

 unknown coasts and waters is much greater. This should demonstrate 

 clearly the vast field of labor awaiting the maritime surveyor. 



England perseveres in this work, and her hydrographic parties are 

 found in every quarter of the globe, opening new channels to com- 

 merce, and defining the dangers of navigation. France, in her publi- 



