TRANSACTIONS OP THE SECTIONS. ^9 



entire breadth of the Pacific between the latitudes of 4° or 5° and 10° North. Only 

 one small portion of its course had been previously noticed. Without quoting the 

 observations here, it may be stated that, proceeding from west to east, the remarks 

 and experience of Krusenstern, Duperrey, Liitke, Hunter, Wilson, the U.S.. Explo- 

 ring Expedition, Du Petit Thouars, the Prussian ships Mentor and Princess Louise, 

 Liitke again, the Dutch frigate Koerier, Beechey, and Vancouver, besides other facts 

 drawn from natural phaenomena, will demonstrate its almost permanent existence ; 

 and these observations are almost all authentic, and above suspicion. 



The current system which thus centres at Panama is most singular, and, as far as 

 known, is unexampled : the only approximation to a similar position is in the Bight 

 of Biafra. We have here the waters of the equatorial counter-current, frequently 

 those of the Peruvian current from the southward, and of the Mexican currents 

 almost always from the northward. The outlet as a surface current to these great 

 masses of water does not seem to have been detected as yet. 



In assigning a cause or combination of causes for these mighty operations, we are 

 met with many and, at present, insuperable difl5culties. Our knowledge of many 

 most material facts is most incomplete. We know little or nothing of the maximum 

 density of sea water. Dr. Marcet places it at a temperature of 22° Fahr., M. Erman 

 at 25°, Col. Sabine at 42°, and Sir James Ross at 39°"5. The latter states that the 

 zone of equal density arising from temperature is in a mean lat. of 56° 26' S. 

 Whatever may be its maximum density, it is certain that we can sink a sounding 

 weight to an enormous depth (8| miles of line having been run out), but the author 

 did not admit the experiment as satisfactory, and concludes that it has not informed 

 us of the depth of the ocean. We know little of the ratio of absorption and radiation 

 of heat — a most powerful cause. The effect of the rotation of the earth is difficult to 

 be calculated without these additional elements, nor can the accumulated action of 

 tides, if any, be estimated, though more exact and extended observations will doubtless 

 enable us to integrate all these sources of motion, and assign to each its amount of 

 action. 



The action of the wind, it was maintained, was the chief and efficient source of 

 surface current action, and a diagram of the trade and passage winds was offered to 

 explain this. Thus the north-east and south-east trade-winds, blowing towards the 

 equator, impel the surface waters in the same direction ; but the winds meeting, neu- 

 tralize each other as to horizontal motion, and rise up, depositing their great moisture 

 in the deluges of the equatorial rains. From the fact of the unequal distribution of 

 land and water in the two hemispheres, — in the south the proportion being 100 land 

 to 628 water, and in the north 100 to 154, — this line of junction is to the north of 

 the equator ; thus the mathematical and atmospheric equators do not coincide. The 

 countries in south latitudes are as remarkable for dryness as those in north are for 

 wetness; and Panama, lying in this junction, is inundated with rain during the 

 northern summer, — sufficient water falling to feed the high level of any canal that 

 may be made with locks. 



From the waters being impelled thus to the western side of each ocean, it might 

 readily be argued that the Atlantic would be several feet higher than the Pacific, 

 and such was formerly supposed to be the case ; but engineering operations have 

 shown that they are sensibly the same ; and this equality of level must be owing to 

 the compensative efi^ect of the equatorial counter-current. 



The great utility of a proper knowledge of ocean currents may be made evident by 

 an example. A ship sailing from Shanghae in China to Panama, may in ignorance 

 follow the apparently direct course, a distance of 8982 miles ; but her voyage would 

 be extended by adverse winds and currents (the latter 600 or 800 miles) to the 

 extent of not less than 1800 or 2000 miles. But if our acquaintance were more 

 complete, and analogy be borne out by facts, by taking a proper course, of about 

 9500 miles, she would be assisted 900 miles in her course by current and fair 

 winds, — thus making the unknown voyage 11,000 miles, and that on correct prin- 

 ciples 8600, a difi"erence worthy of being appreciated in this commercial age. Again, 

 as to the influence of ocean currents upon commercial products. The famous Sea 

 Island cotton of the United States owes its superiority to the warm waters of the 

 Gulf-stream flowing past these sea islands. The trade-wind, passing over the Gulf- 

 stream, and absorbing its saline vapours, deposits them on the sea coasts in ques- 

 tion, and causes the peculiar growth of the long-stapled sea- island cotton. The 



