ll<3 On the Surface Temperature and Great Currents 



the meridian of 62-G4° W. : 4. Up to longitude 40° the sur- 

 face temperature never descended below 50° ; — the average 

 lowest of the sixteen meridional sections being 51 0, 88, and 

 the average range 1L°*3 : 5. In the succeeding fifteen sec- 

 tions, where the lowest temperature was 32°, the average 

 lowest was 37°1 and the average range 29°*7. This re- 

 markable difference in the temperature of the eastern and 

 western halves of the Atlantic passage, the author said was 

 conclusively indicative of great ocean currents yielding a 

 mean depression of the lowest meridional temperature from 

 51°-88 to 37°1, or 14°*8, and producing a mean range of the 

 extreme of temperature on the western side of almost thrice 

 the amount of the extremes on the eastern side, — or, more 

 strictly, in the proportion of 29°- 7 to 11°*3. The author drew 

 attention to a diagram in which he had laid down along the 

 entire belt curves shewing the whole range of the lowest de- 

 pressions of temperature and highest elevation, with the means 

 at each longitude distinguished by different shading ; and 

 pointed out how the inspection of this as well as of the tabu- 

 lated results affords striking indications of the two great cur- 

 rents, one descending from the polar, the other ascending 

 from the tropical regions, with their characteristic changes 

 of cold and heat. In classifying the results, the author con- 

 sidered the entire belt of the Atlantic track of the passages 

 as divided into six divisions of 10° of longitude each, and these 

 into meridional stripes of 2° each, omitting the first two de- 

 grees next the European end, or about 80 miles westward of Ire- 

 land to 72° W., or about the same distance west of New York. 

 To each of these six divisions he directed attention, pointing 

 out the conclusions to be derived from each. The curves 

 approaching each other and running nearly parallel through 

 the western half with great regularity, shewing the variations 

 and range to be much less, while throughout the eastern half 

 the widening of the distance, and the irregular form of the 

 extreme curves shewed the influences of the two currents very 

 remarkably. The author then proceeded to draw conclusions, 

 shewing that sometimes the cold current from the north 

 plunged beneath the warmer current from the south. Some- 

 times they divided, — the colder keeping in-shore along the 



