APPENDIX. 
525 
On ship-board .] 
It appears that differences, probably similar to those in the Investigator, 
were also observed on board La Recherche , one of the ships with which 
the French admiral D’Entrecasteaux went in search of the unfortunate La 
Perouse. Monsieur Beautemps-Beaupre, the able surveyor to the ex- 
pedition, found so much uncertainty in compass bearings that he abandoned, 
as far as was possible, the use of them ; substituting the sun’s azimuth and 
angular distance from some one point, and measuring the angles from that 
point to other objects. He says of the compass, “ We found by a great 
“ number of observations, but principally by the differences between the 
“ bearings of points set with each other from opposite directions, that no 
* c confidence could be had in bearings taken with the compass from the 
“ deck of a Inrire vessel, nearer than to 3°, even under the most favourable 
“ circumstances. For instance, it has often happened that from one 
“ position, as C, the cape A has been set. in a line with cape B ; and after- 
“ wards, from another position, 1), cape B has been set with A ; and that 
£C we have found considerable differences in the results of the two obser- 
(t va tions.* We also remarked, that the compass showed differences of 
£C several degrees in variations at sea, though observed with the greatest 
“ care and within the space of a few*minutes,” (Voyage de I) Enlrecas- 
teaux, par M. de Rossel. Vol. I. p. 600. A Paris, 1808.) 
Ido not find any other distinct mention of differences found in the 
variation , from changing the direction of the ship’s head or the place of 
the compass ; but it appears from the following extract, that the Inves- 
tigator was not singular in having a variation of 4°. greater than the truth 
in the English Channel. Captain Vancouver, in his passage towards 
Madeira, says (Vol. I. p. 6.), “ The error in reckoning, am uniting almost 
“ to a degree (of longitude), seemed most likely to have been occasioned 
“ by our not having’ made sufficient allowance for the variation of the 
“ compass on our first sailing; as, instead ol allowing from 22° to 25 , 
« w hich was what, we esteemed the variation, our observations for ascer- 
taining this fact, when the ship was sufficiently steady, shewed the 
“ variation to be 28° and 29|° wcstwardly. 
* In .he sketch given for elucidation, the ship at the position C,is represented to be 
steering S. W., and at the position D, N. by E.; hence probably the difference of 
bearing. 
