Narrative of the surveying voyages of his majesty's ships Adventure and Beagle (vol.2- Appendix): between the years 1826 and 1836 : describing their examination of the southern shores of South America, and the Beagles's circumnavigation of the globe

330 APPENDIX. to state, that in no one instance did it differ a quarter of a second from theirs ; indeed the figures would bear me out in saying, that it did not differ even a tenth of a second ! These facts are well known to Lieut. Stokes, Lieut. Suhvan, and Mr. Usborne. The sextant used throughout the voyage for this purpose, and this alone, was a particularly good one, made expressly for me by Wor- thington and Allan. Its index error never varied, nor was it ever the least out of adjustment. Between morning and afternoon observa- tions it was more than usually guarded, and on no accotmt handled, or exposed to a change of temperature. Latitudes were obtained by other sextants, and by circles. I was always anxious to get many results, not only by one observer, or in- strument, but by several observers, and different instruments. It sometimes happened that there were six observers seated on the ground, with as many different instruments and horizons, taking the sun's circum-meridian altitudes, or observing stars at night. Where so many were working against one another, errors were soon de- tected, either in observation or in computing. I have already men- tioned that Dr. Inman's method of calculation was followed ; but it remains to be shown what mode of interpolation was adopted when, as was usually the case, most of the watches were found to be going at rates different from those ascertained at the preceding place of rating. With very few exceptions, the method used by Dr. Tiarks* was practised ; and, in the excepted cases, that used by FHnders, Owen, Foster, King, and others, was employed. The following are the princi])al results upon which all others obtained during the Beagle's last voyage (1831-6) depend. Want of room alone prevents my giv- ing the minutest details upon which they depend ; it would be of little use to give comjDutations without comparisons, or comparisons without rates, or rates without the calculations and observations on which they depend ; or any part of these without the whole, which constitutes a mass of figures filling several thick folio books. All these, however, will be deposited at the Hydrographical Office, so that any one who will take the trouble may, after obtaining the Hydrographer's permission, examine them to the fullest extent. Our first station was at the Devonport Baths, exactly in the meri- * Chanticleer's Voyage — Appendix, p. 226-8.