20 REPORT — 1853. 



perature obtains the first marked increase, indicative of a slight action of a current 

 from the southward. 



In the fourth decimate section, 42" to 52° W., however, the indications respect- 

 ively of the two great currents of the North Atlantic become striking and charac- 

 teristic. Beyond the meridian of 42°, where the cold current from the north becomes 

 first decided, an increase of its ptevalenc)', gradually becoming more and more con- 

 spicuous, is observed. Thus in the two degrees' space, from 42° to 44° W., the 

 somewhat low temperature of 44° was only observed in one out of //nV/een passages ; 

 but in the next two degrees a like moderate fall of temperature (about 7^ below the 

 mean) occurred in three or four of the passages ; in the next meridional stripe, cold 

 water was met with in eight of the passages (four or five falling from 10° to 16° 

 below the mean) ; in the next, the cold water occurred in nine or ten passages (six 

 falling 10° to 24° below the mean) ; in the next stripe, longitude 50° to 52° W., the 

 cold water was met with in eight passages (five falling 12° to 22° below the mean). 



Within the same section, 42° to 52° W., very perceptible marks of an ascending 

 tropical current occurred, yielding, in alternations with the cold water from the north, 

 an occasional warmth of 66° to 68°. The prevalency, however, of the occurrence 

 of warm water in this position of the Atlantic appears from the observations tabu- 

 lated to be in reverse order (when sailing westward from longitude 42°) to that of 

 the cold current ; the first two-degree stripe presenting a rise of from 63° to 68° in 

 six passages ; the next, a rise of similar extent in five ; the next, a smaller rise in four ; 

 the next, less marked in three ; and the last, 50° to 52° W., in four, but still less 

 marked. Hence from these observations it appeared, that the greatest prevalence of 

 the polar currents (betwixt 42° and 52° W.) is within the meridians of 46° and 52°, 

 and of the warmer current in 42° to 46° W. 



It is within this meridional section mainly, corresponding in its central part with 

 the eastern edge of the great bank of Newfoundland, in which the icebergs and drift 

 ice from the north are usually met with ; so that the prevalence of a descending 

 polar current obtains actual demonstration. 



The fifth decimate secfion, reaching from 52° to 62° W., is found to be equally 

 characterized by peculiar phaenomena as the one preceding it. The general preva- 

 lence of the descending polar current is shown by the minimum temperature of each 

 meridional space of 2°, ranging betwixt 32° and 42°, with a mean of the five minima 

 of 37°'2. The prevalence of an ascending current from south-westward is, in like 

 manner, shown by the occurrence of a maximum surface temperature ranging betwixt 

 63° and 74°, with a mean of the five maxima of 68°"9. 



But the characteristic features of this fifth decimate section were found to consist 

 in the sudden7iess of the changes of the surface temperature and the various alternations, 

 indicative of singular interlacirtgs of warm and cold water. 



In a passage in the " Patrick Henry" in May 1844, made by Dr. Scoresby, these 

 sudden and alternating changes were remarkably prevalent. Thus when in longi- 

 tude 57° 0' W. (lat. 41° 31' N.) the surface temperature, at 8 a.m. of May l7tb, 

 was found to be 60°-5 ; but after sailing W.N.W. (true) 10 miles, it was found to 

 be 50°, and at noon 16 miles further on the same course 46°. At 2 p.m. of the 

 same day, longitude 57° 55' W., the sea was still at 46°; but at 4 p.m., after 15 

 miles' sailing W.N.W., it had risen to 57°, and in 15 miles further in the same 

 direction it was found to have fallen to 42°! The next day. May 18th, presented 

 further remarkable changes. At 8 a.m., longitude 59° 52' (latitude 42° 8' N.), the 

 surface temperature was 46°; but at 10 a.m., 15 miles W. ^ S., it had risen to 

 61°, a change of 15° in two hours ! At midnight, again, of the 19th-20th the sea 

 was at 50° ; four hours afterwards, 26 miles to the S.W. by W., it was 63°. 



Within this decimate section the cold or polar current was found to be chiefly pre- 

 valent in the first and last of the two-degree spaces, but the most so in the last, that 

 is, in longitude 60° to 62° W. ; and the most prevalent examples of the Gulf-stream 

 appeared within the meridians of 58° and 62° W. 



The sixth and last section of the belt of waters traversed in the transatlantic pas- 

 sages under discussion, is found to be chaiacterized, especially within the three 

 westernmost spaces, 66° to 72° W., by a singular depression of the surface tempera- 

 ture generally, the mean temperature of all the observations registered on the chart 

 being 49°'4, and of the last three stripes 46°'7. As some of the voyages, however. 



