NARRATIVE OF THE CRUISE. 
755 
considerably lower than those obtained at corresponding depths at Stations 239 and 
241 on either side of Station 240. Thus, at 100 fathoms the temperature at Station 240 
was 15° lower than at Station 239, and 12° lower than at Station 241 ; at 200 fathoms 
it was 16° lower than at Station 239 and 10°‘3 low ? er than at 241, &c., down to 
1500 fathoms, at which depth the same temperature was obtained as at all the other 
Stations. A further peculiarity here was, that from 200 to 300 fathoms the water was 
at a temperature of 40°. 
The upper isothermal lines between the coast of Japan and Station 240, 650 miles 
from the coast, occupied greater depths than they did between Station 240 and the 
180th meridian, being doubtless influenced by the Japan Current. The isotherms were 
fairly parallel with the surface (see Diagram 17). 
The abnormal condition of the temperature at Station 240 is due in all probabi- 
lity to an outset from the Sea of Okhotsk, or the western part of Behring Sea, as 
Captain Belknap, in the U.S. ship “ Tuscarora,” found a belt of cold water opposite the 
entrance of those seas, which, from the observations of the Challenger, appears to extend 
to the 35th j)arallel. Here however it nearly ceases, as the width of the cold stream 
on the surface did not exceed 20 miles. 
The serial temperatures taken on the 38th parallel, between the meridian of 180° 
and 156° 25' W., gave nearly the same results, so that the isotherms were fairly 
parallel with the surface, the isotherm of 40° being at an average depth of 400 
fathoms; that of 45°, at an average depth of 250 fathoms; of 50°, at 150 fathoms 
(see Diagram 18). 
In the third part of the section, from a position in lat. 38° 9' N., long. 156° 25' W., 
to the Sandwich Islands, the upper temperatures increased as the vessel proceeded to 
the southward, causing the isotherms above 50° to descend gradually ; the isotherms of 
40° and 45°, however, maintained a position nearly parallel with the surface, at depths 
of 400 and 250 fathoms (see Diagram 19). 
No current observations w T ere taken by mooring a boat to the sounding line or 
trawl rope, but whilst sounding or trawling the direction of the surface set was noted, 
and its velocity estimated ; and the direction and rate of the current were also calculated 
from frequent astronomical observations. The general direction of the current from the 
Japanese coast to the meridian of 170° E., was northeast 19 miles per diem, the 
greatest set in any one clay being 37 miles, and the least 10 miles. From the meridian 
of 170° E. to 156° W. the currents were variable and generally insignificant, and on the 
southward track to the Sandwich Islands they were variable between the 38th and 30th 
parallels, and had a general westerly tendency from the 30th parallel to Oahu, the 
velocity being in no case considerable. 
Anemometer observations were taken wdien favourable opportunities offered, whilst 
the ship was stationary sounding or trawling ; and it was also noticed that the direction 
