APPENDIX. 
451 
By means of the system of signals prepared by me for the Ex- 
ploring Expedition, I could direct the vessels to assume any position 
I might select as most fit for our purpose. When these were reached, 
general, but minute instructions, directed the observations that were 
to be taken at each, in doing which there was no difficulty. These 
observations were entered upon a deck-board, for which the following 
form was prescribed : 
FORM OF DECK-BOARD. 
TIME. 
POSITION. 
TIME. 
AZIMUTH 
OF 
LEFT-HAND 
OBJECT. 
CENTRE 
OBJECT. 
RIGHT-HAND 
OBJECT. 
REMARKS. 
To illustrate still further the mode in which the whole squadron 
was made to concur in obtaining unity of action, a detail of a survey 
and a plot of the work are subjoined. 
On approaching the island to be surveyed, signal was made to 
prepare for surveying duty ; if boats were to be used, the number 
of them and the vessels whence they were to be despatched was next 
indicated; and finally, the position each vessel was to occupy was 
shown. The vessels having reached their assigned places hove-to, 
and the boats, having been previously despatched, would about the 
same time have anchored in their assigned stations, at the points of 
reefs, and hoisted their appropriate signals. The vessel that is 
first to fire a gun then hoists an ensign at the foremast-head, which 
is answered by all, and the flag is in like manner displayed previous 
to each successive fire. The firing then goes on in quick succession 
from all the vessels; and during the time, or immediately after, all the 
officers being on deck for the purpose, angles are measured between 
one of the other vessels and objects on the shore, each by a different- 
observer, as directed and indicated by the oldest officer on the deck. 
The objects on a coral island are always few and distinct, and these 
angles, together with those made by the visual tangents to the shores, 
have always been found sufficient to plot from. During this opera- 
tion the ensign is kept hoisted at the peak, so that the angles from the 
several vessels may be taken simultaneously. Altitudes of the sun 
for time, and angles whence to calculate the azimuth of some one of 
the objects, are also taken immediately before or after the horizontal 
