in all probability will be different at the two observations.
With an artificial horizon, indeed, the changes in refraction
are not felt, because, at a considerable elevation above the
horizon, the changes are very trifling. But it often happens
in practice, that the artificial 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 a t 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.
I t is much to be wished that this excellent instrument
should be brought into general use in navigation.
T H E FOLLOWING E IG H T OBSERVATIONS AR E SET DOWN
IN T H E FU L L E ST D E TA IL , IN ORDER TO SHEW TH E
METHOD USED IN RECORDING THEM.
No. 31.
YELLOW SEA.
Ju ly 2 3 ,18Ï6.—6 P. M.
Index uppermost. Instrument inverted.
¡Üa8Ü . n05ai 1 I
8 . 00 E M
a s + i - . s t
15 .1 5
Height of the eye, 15 feet, 8 inches.
Parts of the horizon observed, WSW. and ENE.
Barometer - 29 . 78 inches
Thermometer if Ageiar 817270°
Latitude - - 35° north.
Longjtude - 124° east.
Wind light from south; horizon uncommonly well defined and sharp; sky clear,
and sea perfectly smooth.