366 EXPEDITION TO JAPAN. 



facts disclosed by the observations now under consideration, for in the winter of 1848, when 

 attached to the United States ship Preble, commander James Glynn, and bound from Hong 

 Kong to Japan, we struggled for three days, after leaving the port, against this southwest 

 current, setting down through the Formosa channel, without making a single mile on our 

 course to the eastward, and were compelled to resort to the expedient of working along in-shore 

 and anchoring whenever the tide was combined with the current against us. A number of days 

 were thus toilsomely spent before reaching Breaker Point, on the coast of China. We then 

 stretched across the channel, in the middle of which we felt the full strength of the southwest 

 or counter current. But on doubling the south end of Formosa we immediately fell into the 

 Kuro-Siwo, and were borne by it ninety-two miles, dead to windward, in less that three days, 

 whilst lying-to, under storm sails, in a stiff gale from the northward and eastward. 



The diagrams, you will perceive, show an increased temperature of both the air and the 

 water the moment this stream is entered, but a predominant thermal change in the water, 

 which almost invariably continues superior in temperature to that of the air until leaving the 

 stream again. On the northwestern edge of the stream the transitions are sudden and extreme, 

 varying, according to the latitude, from 10° to 20°. On the southeastern side the change is 

 less abrupt, and, from the gradual approximation of the thermal ranges of the air and water, 

 its outline is rendered less distinct and definite. 



Along the borders of the stream where it chafes against the torpid waters of the ocean and 

 counter currents, as also in its midst where whirls and eddies are produced by islands and the 

 inequalities in its bed, strong tide-rips arc constantly encountered which often resemble heavy 

 breakers on shoals and reefs, and become finger-boards, as it were, to warn the seaman of the 

 otherwise unseen influence which may be bearing his ship far from her intended track, and, 

 perchance, upon some of the many fearful dangers that sprinkle that region of the sea. 



The Gulf stream, as delineated in the Coast Survey Report of Professor A. D. Bache for 

 1854, I have copied upon the chart, in order to exhibit to the eye the striking resemblance 

 between it and the Kuro-Siwo. The former is the result of the observations made upon that 

 stream by the coast survey under the direction of Professor Bache. The latter is delineated 

 entirely from the reports and observations made by the Japan Expedition ; and, as these latter 

 were obtained during the necessary transits of the vessels from port to port in the discharge of 

 their duties connected with the expedition, they cannot, of course, in any manner pretend to 

 the same comprehensive accuracy and conclusiveness as those upon the Gulf stream ; yet they 

 are sufficient, as I have before stated, to prove the remarkable analogy, in almost every par- 

 ticular, between these two important currents of the Atlantic and Pacific oceans. 



The strata of cold water lying in the longitudinal direction of the streams, as represented on 

 the chart, were traced upon the Kuro-Siwo from the diagrams of Plates V, VII, XIII, XV, and 

 XVI. I am not precisely aware of what the thermal change is in passing into or from these 

 cold strata in the Gulf stream ; but those in the Kuro-Siwo were indicated by a depression of 

 only a few degrees in the water thermometer, and should more properly, perhaps, be termed cool 

 strata, as compared with the rest of the stream ; for in all instances these strata maintain a 

 superior temperature to the atmosphere above them ; and if the hyperborean current is, as I 

 have supposed, entirely separated from the Kuro-Siwo by its passage through the Straits of 

 Sangar to the westward of Japan, I am inclined to think that there is no counter current under- 

 lying the Kuro-Siwo, as is the case with the Gulf stream. This, however, can be determined 

 only by experiments with the deep-sea thermometer, and the usual apparatus for determining 



