452 
APPENDIX. 
angles ; and in the boats, if sufficiently near, the altitude and azimuth 
of the mast of one of the ships is observed at the same time, for the 
purpose of defining the boat's position. 
When this is done, one of the vessels quits her position, while 
the others maintain theirs by manoeuvring so as to keep the angles 
between objects on the shore of the same magnitude; and having 
attained a new position, the same operations are repeated, the boats 
having in the mean time, also, changed theirs, and anchoring as soon 
as the vessel takes her new station. When anchored, the time that 
elapses between the flash and sound of the guns, and the angles 
between the vessels, are again observed. By such alternate changes 
in the stations of the several vessels, continued until a circuit of the 
island has been made, the work is finished, and when it joins, it is 
proved by the last distance determined by azimuthal angles and 
sound, as by a base of verification. The deck-boards are now sent 
on board the flag-ship, where the work is calculated and plotted. 
Of such an operation, the annexed wood-cut is an example. 
Hy.* 
The survey of the island thus represented, which is about seven 
miles in length, was performed in three hours and thirty-five minutes. 
