Geography 



487 



the chronometer — have thus placed in 

 the hands of sailors ready means of fix- 

 ing with great exactitude and celerity 

 the position of selected points on coasts 

 all over the world ; and it will be seen 

 that, while the detail of the line of coast 

 between such fixed positions will de- 

 pend upon the degree of accuracy of 

 the survey or sketch, the general line 

 cannot get far out, as it is constantly 

 checked at the selected points. 



It is not claiming too much to say 

 that at the present time very few salient 

 points on the coast lines of the world 

 are as much as two miles in doubt. 



It should be a source of great satis- 

 faction to the Briton to know that both of 

 these instruments were devised by Eng- 

 lishmen, John Hadley producing the 

 sextant in 1730, in the form still used, 

 on the basis of ideas formulated by New- 

 ton fifty years before, and John Harri- 

 sion the chronometer in 1736. The 

 latter instrument has undergone modi- 

 fications in detdil, but the principle re- 

 mains the same. It required seventy 

 years before its value was fully recog- 

 nized and it came into general use. 



MARINE SURVEYS BY BRITISH NAVAL 

 OFFICERS 



It is a still further satisfaction to think 

 that it is British naval officers who have 

 made by far the greatest use of them in 

 mapping the coasts of the whole world. 

 Since the time of the great Captain Cook , 

 British surveying vessels have been con- 

 stantly employed in this work, not only 

 in British colonies, but in all parts, aid- 

 ing and often paving the way for British 

 commerce and for the men-of-war that 

 protect it. 



It is difficult to find coasts of any ex- 

 tent that have not been laid down by 

 British marine surveyors. The whole of 

 Africa has been their work. By far the 

 greater part of America, all the south 

 and east coasts of Asia, Australia, and 

 most of the innumerable islands in all 

 oceans have been fixed and laid down 



by them. Even in the Mediterranean, 

 until very lately, the charts were mostly 

 founded on British surveys, and the im- 

 provements now being carried out by 

 other nations on their own coasts in de- 

 tails required for modern navigation do 

 not materially modify the main shapes 

 and positions formerly determined by 

 the British. 



It has been, and is, a great work, and 

 I hope I may be pardoned for dwelling 

 on it with pride as the result of the 

 wise administration of the admiralty 

 for many years, and of the immediate 

 labors of my predecessors as hydrog- 

 rapher, and as a very great contribu- 

 tion to geographical knowledge, more 

 especially as I do not think that it is gen- 

 erally realized that this great advance in 

 geographic accuracy is due to marine 

 surveyors. 



To give an idea of the comparative 

 accuracy of the chronometer method, I 

 may mention that on taking at hazard 

 eleven places distributed all over the 

 world at great distances from England, 

 the longitudes of which have been re- 

 cently determined by means of the elec- 

 tric telegraph and elaborate series of 

 observations, I find that the average dif- 

 ference between the chronometer and the 

 telegraph positions is 700 yards. The 

 shapes of the different continents and 

 the positions of islands as at present 

 on our maps and charts will never be 

 altered except in insignificant degree, 

 and the framework is ready for many 

 years' work of land mapping. 



THE PERILS OF THE DEEP 



It is not to be inferred from what I 

 say that marine surveys are approach- 

 ing their close. It is far otherwise. The 

 time given to these enormous extents of 

 coasts and seas and the necessarily small 

 scales on which the surveys have been 

 carried on have caused them to be very 

 imperfect in all details. Hundreds of 

 rocks and shoals, both stretching from 

 the land and isolated in the sea, have 



