TRANSACTIONS OF SECTION E. 44.9 
error when a number of chronometers are employed. These two simple yet 
marvellous instruments, the sextant and the chronometer, have thus placed in the 
hands of sailors ready means of fixing 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 depend 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 satisfaction to the Briton to know that both 
these instruments were devised by Englishmen, John Hadley producing the 
sextant in 1730, in the form still used, on the basis of ideas formulated by 
Newton fifty years before; and John Harrison the chronometer in 1736. The 
latter instrument has undergone modifications in detail, but the principle remains 
the same. Seventy years elapsed before its value was fully recognised and it 
came into general use. Pa 
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 constantly employed in this work, not only in British colonies, but in all 
parts, aiding 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 extent 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, till very lately, the charts were mostly founded 
on British surveys, and the improvements now being carried out by other nations 
on their own coasts in details 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 labours of my predecessors as Hydrographer, and as a 
very great contribution to geographical knowledge, more especially as I do not 
think that it is generally realised 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, whose longitudes have been recently determined by 
means of the electric telegraph and elaborate series of observations, I find that the 
average difference 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. 
It is not to be inferred from what I say that marine surveys are approaching 
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 been missed, 
and loss of ships and life on these unknown dangers still continues. With the 
increase of shipping, increased number of ships of heavy draught, the closeness 
of navigation due to steam, and the desire to make quick passages, smaller in- 
accuracies of the charts become yearly of greater importance. 
As an illustration of the condition of affairsI may mention that in Hamoaze, the 
inner harbour of Plymouth, one of the headquarters of the British fleet for over 
300 years, a small but dangerous pinnacle of rock was only discovered five 
years ago; whilst numerous other dangers of a similar character haye been 
yearly revealed in close surveys of other harbours in the United Kingdom, supposed 
to be well examined and charted in the last century. 
1905, Gd 
