Joty—Altitude of Celestial Olject at Sea at Night-Time. 567 
The “ double chronometer problem ” may be also worked, using 
one assumed latitude only, and finding the lines of position by 
finding true bearings by Azimuth tables, using the declinations 
and calculated hour angles in the usual manner. 
I have not in the title of this paper altogether restricted the 
method to observations made at night-time. In hazy weather, 
which at the same time may very probably be calm weather, the 
method is applicable to taking approximate altitudes of the sun. 
_ In this case the most suitable object to use as a signal would be a 
spherical or hemispherical bright tin float, but, as such must be 
specially provided, the use of any fairly bulky and conspicuous 
object might be resorted to successfully: as a piece of plank with 
an upright attached and a shape of any kind on top. This being 
“‘anchored”’ by a length of a few fathoms of marlin and attached 
sinker, is used asa signal. An ex-meridian (or meridian) observa- 
tion is best made by sailing from the signal in the manner before 
described, and when a suitable distance is attained reading the 
elevation and noting time by “ watch.” 
SCIENT. PROC. R.D.S., VOL. IX., PART V. 2x 
