NARRATIVE OF THE CRUISE. 
749 
reaching its minimum at 4 a.m. on the 4th (29 ’48 inches), then rising quickly, with 
a freshening wind from the northeastward. 
On the 4th, at 7.30 a.m. the mist cleared, the weather became quite bright, 
and the land about Matoya was distinguished; astronomical observations were also 
obtained by which it was ascertained that no current whatever had been experienced 
since passing Hino Misaki. At 4 p.m., the weather being very fine and calm, a sounding 
in 565 fathoms, serial temperatures, and a most successful and productive trawling were 
taken in lat. 34 c 7' N., long. 138° 0' E., and again no current was found running 
(see Sheet 35). At 7.30 p.m. the vessel proceeded under steam towards Rock Island. 
On the 5th June at 8 a.m. Rock Island lighthouse was passed, and at 1 p.m. a 
sounding, trawling, and temperatures were taken in depths varying from 775 to 420 
fathoms over rocky uneven ground, with the left extremity of Vries Island S. 9° W., 
the right extremity of Vries Island S. 32° W., and Tree Hill N. 42° W. Considerable 
difficulty was experienced in recovering the trawl, owing to the rocky nature of the 
bottom, but eventually it was hove to the surface at 5 p.m. much torn and containing a 
few stones, after which the ship proceeded for Yokohama, anchoring there at 9 p.m. 
The Japan Stream or Kuro Siwo. — The Challenger’s observations show that on 
approaching Japan a belt of water which was running to the northeastward at the rate 
of three miles per hour was passed through between lat. 32° 30' N. and 33° 30' N., on 
the meridian of 138° 25' E. from Greenwich. On the southern edge of this belt the 
stream had a more northerly, and on its northern edge a more easterly, tendency than 
N.E. When to the northward of this belt of rapidly moving water a set of one mile per 
hour was experienced. 
When in the current the temperature of the surface water varied from 63° to 68°, 
changing suddenly from the one temperature to the other, giving alternate streams of 
cold and warm water without any alteration in its rapidity being detected. That this 
was the case is readily proved by the observations from 7 a.m. to 10 p.m. on the 10th 
April, which, though taken at different times, all agreed in showing a steady set of 
three miles per hour, although the temperature of the sea changed suddenly at 1 p.m. 
from 68° to 64°, and at 7 p.m. from 63° to 68°. 
In the month of May a moderate set to the eastward was experienced close to the 
south coast of Nip on Island. In June there was no current at a distance of 30 to 40 
miles from that coast, but to the southeastward of Nipon a stream was found running to 
the northward at the rate of two miles per hour of the mean temperature of 7 2° '5. 
The rapid stream of alternate belts of warm and cold water south of Nipon Island 
probably originates in the following manner : — The northern Equatorial Current striking 
against the eastern side of the Philippine Islands is, as is well known, diverted to the 
northward, along the eastern side of Formosa, after passing which, it appears gradually 
