APPENDIX. 207 



number of inferior marks ; by a ' round ' of angles taken with a 

 theodolite, at each station (B and C), the instrument being in each 

 case set to A. From A, the true bearings of B and C were ascertained 

 astronomically. When the position of L was exactly determined by 

 latitude, and distance from the meridian of A, the long and accu- 

 rate base AL became known. With that, as a foundation, the work 

 was laid down : and by that base, if necessary, the former positions 

 of G, D, E, and F, were corrected. But so well did angular mea- 

 sures answer, that it was scarcely ever requisite to make such cor- 

 rections. 



It has been shewn that the log served only to place soundings, or 

 help to fill up a space, while clouds obscured marks. I should add 

 that it was serviceable in ascertaining the direction and strength of 

 currents. Currents altering in strength, as well as in direction, 

 prevented our applying the patent log to other uses, although we 

 had every reason to put implicit confidence in its indications, and 

 have often proved their value in the still waters of a deep sound, 

 where no stream of tide^ or current, existed : as well as in harbours, 

 where angular bases were measured for the special purpose. Views 

 of the lands, both in plan and profile, were very frequently taken. 

 When boats could be lowered, and a sufficient object demanded their 

 employment (as at 11, of the first day, and at 10 of the second day) 

 they did not hang idly at their davits. 



In the example I have given, circumstances conspired in our 

 favour, a rare event in Tierra del Fuego, or on any similar coast, 

 exposed to the prevailing westerly winds of high latitudes ; but when 

 we failed to find anchorage, the triangulation was carried on by first 

 class marks ; and by the ship's positions, when fixed by good observa- 

 tions at sea. But however well such a method may answer in a fine 

 climate— on that coast it was in general unsatisfactory, and very 

 inferior to that of going from one harbour to another. 



Among many kinds of notation useful in svirveying, the annexed 

 sketch shews a method used by Mr. Stokes, which I had not then 

 seen adopted. It is very convenient, and assists the memory more 

 than any other. In figure 2, A and B are stations, at which the 

 angles specified were taken right and left of a mark, whose bearing 

 was ascertained. Or, the angles only were taken, and the triangles 

 afterwards calculated, or protracted, by reference to the base upon 

 which they depended, such as AB. A sketch on this principle, how- 



