334 Capt. Sabine on the Presence of the Water 
land to Madeira, were observed to differ from each other half 
a point in one direction when on south-westerly courses, and 
less than half a point in the opposite direction when on easterly 
courses, the indications of the compasses having crossed each 
other, and agreed at some intermediate point; it was requisite, 
therefore, that the correction to be allowed on every course 
by each of the two compasses should be ascertained, and that 
the compass by which each course was directed should be 
specially recorded, in order that the true course should be 
known. 
The most obvious mode of preventing so much inconyve- 
nience and trouble, as well as the more correct practice, is to 
direct and note the ship’s course by one compass only, sta- 
tioned permanently in some convenient situation, without re- 
ference to the helmsmen, and to use the binnacle compasses 
solely to steer by, on the point which may be noticed at the 
time to agree with the magnetic course of the standard com- 
pass; and by employing an azimuth compass for the latter 
purpose, the advantage is gained of enabling the variation to 
be observed directly with the compass by which the course is 
governed, and thus of avoiding intermediate comparisons, in 
which time is occupied, and errors frequently introduced. 
This arrangement of a standard compass was adopted by 
Captain Clavering in the Pheasant, and subsequently in the 
Griper, and was found to answer its purpose perfectly, and to 
be attended with no practical inconvenience whatsoever. 
Although from the courses above noticed, no satisfactory 
investigation of the direction or velocity of currents could be 
made in the Iphigenia, in her passage from England to the 
coast of Africa, a remarkable and very interesting evidence 
was obtained by observations on the temperature of the sea, of 
the accidental presence in that year of the water of the Gulf- 
stream, in longitudes much to the eastward of its ordinary ex- 
tension. The Iphigenia sailed from Plymouth on the 4th of 
January, after an almost continuous succession of very heavy 
westerly and south-westerly gales, by which she had been re- 
peatedly driven back and detained in the ports of the Channel. 
The following memorandum exhibits her position at noon on 
each day of her subsequent voyage from Plymouth to Ma- 
deira, and from thence to Cape Verd Islands, the tempera- 
ture of the air in the shade and to windward, and that of 
the surface of the sea; it also exhibits in comparison, the or- 
dinary temperature of the ocean at that season, in the respec- 
-tive parallels, which Major Rennell has been so kind as to 
permit me to insert on his authority, as an approximation 
founded 
