diurnal Variation of the Barometer between the Tropics. 183 
taken from Canton to the ship, we were four days in getting 
clear of the river, in which time the mercury inclined to be 
stationary, excepting that a small inclination towards the equa- 
tropical motions seemed to evince itself at times. But no 
sooner had we cleared Canton river, September 13th, 1803, 
than the mercury in the barometers began to conform to the 
equatropical motions, of two elevations and two depressions 
every 24 hours, at equal intervals of time, (although we were 
near the land until the 15th September.) And the mercury, 
with great regularity, continued to perform the equatropical 
motions, from September 13th, 1803, the day we cleared the 
river of Canton, until October 13th, when we entered Sincapore 
Strait, excepting a small degree of irregularity, which affected 
the mercury on the 2 2d September, when it blew a gale on 
the coast of Isiompa. 
October 13th, 1803. On entering the Strait of Sincapore, 
which is about 3-- leagues wide, the mercury in the barometers 
was then a little obstructed, and did not perform the equatro- 
pical motions, in the same quantity of rise and fall, as when 
we were in the China Sea. But on the following day, October 
14th, when we had passed the narrow part of the Strait, the 
mercury conformed to those motions with regularity until 
October 21st, when we arrived in the harbour of Prince of 
Wales’s Island ; then a great retardation took place in the 
equatropical motions ; for, during the time the ship remained 
in the harbour, from October 20th to November 5th, 1803, the 
mercury in barometers seemed only in a small degree subject 
to them, the difference between the high and low stations of 
the mercury, being in general not more than half the quantity, 
that takes place in the open sea, or at a considerable distance 
