Excerpt: ...horizon cannot be used, and we are then reduced to the sea horizon, where the changes of refraction are always the greatest. In the Yellow Sea, for instance, we had no opportunity of landing during all the time that the squadron was at anchor, till the day before we sailed. So that during nearly a fortnight that the ships were at anchor, the sea horizon was necessarily used. I need only to refer to the observations taken off the Pei-ho, viz. from No. 37 to 62, to shew how extremely fallacious the results must have been. It is much to be wished that this excellent instrument should be brought into general use in navigation. THE FOLLOWING EIGHT OBSERVATIONS ARE SET DOWN IN THE FULLEST DETAIL, IN ORDER TO SHEW THE METHOD USED IN RECORDING THEM. No. 31. YELLOW SEA. July 23, 1816.-6 P.M. Index uppermost. Instrument inverted. A + 8'. 10" B - 7'. 10" 8 . 05 7 . 10 8 . 00 7 . 10 --- --- Mean 8 . 05 Mean 7 . 10 B. Mean + 8 . 05 A. ---- 15 . 15 ---- 3 . 49 Dip. 3 . 50 Tabular. 1 Difference. ---- Height of the eye, 15 feet, 3 inches. Parts of the horizon observed, WSW. and ENE. Barometer 29 . 78 inches Thermometer Air 82º Sea 77º Latitude 35º north. Longitude 124º east. Wind light from south; horizon uncommonly well defined and sharp; sky clear, and sea perfectly smooth. No. 40. OFF THE PEI-HO,...
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