216 AXXUAL OF SCIENTIFIC DISCOVERY. 



sensitive preparations, by means of which the absorbing power of various 

 media with respect to these rays might be determined by merely inter- 

 posing, any where in the path of the rays, a plate of the substance to be 

 examined. 



ON THE SURFACE TEMPERATURE AND GREAT CURRENTS OF THE 

 NORTH ATLANTIC AND NORTHERN OCEANS. 



The following communication was read before the last meeting of the 

 British Association by Dr. Scoresby. The observations generalized upon 

 by the author had been derived from the temperature of the ocean, chiefly 

 at the surface, and made in the Greenland Sea, the North Sea, and a 

 considerable belt across the North Atlantic, during a series of passages 

 chiefly by sailing vessels between England and New York. Dr. Scoresby 

 directed the present attention of the Section to the observations made in 

 the last of these localities. Of the passages just noted, sixteen in number, 

 four were performed by the author, and twelve by ail American navigator, 

 Capt. J. C. Delano, an accurate scientific observer. The observations on 

 Surface Temperature discussed amount to 1153, gathered from about 1-400. 

 Usually Capt. Delano recorded six observations each day during the voy- 

 age, at intervals of four hours. Seven of the passages were made in the 

 spring of the year, two in the summer, one in autumn, and three in 

 winter. Taking the middle day of each passage, the mean day at sea was 

 found to be May 18th or 19th, a day fortunately coincident in singular 

 nearness with the probable time of the mean annual oceanic temperature. 

 The author had laid down the tracks of the ship in each of the voyages on 

 a chart of Mercator's projection, and the principal observations on Surface 

 Temperatiire were marked in their respective places. The observations 

 were then tabulated for meridians of 2 C in breadth, from Cape Clear, Ion-' 

 gitude 10 W., to the eastern point of Long Island, longitude 72 W., 

 embracing a belt of the average breadth of 220 miles, or a stretch of about 

 2600 miles across the Atlantic. The results were the following : 1. High- 

 est Surface Temperature northward of latitude 40, 74 ; lowest 32 ; 

 range 39. 2. Mean Surface Tern per ature, as derived from the means of 

 each meridional section, 56, whilst the mean atmospheric temperature for 

 the corresponding period was 54. 2. 3. Hange of Surface Temperature 

 within each meridional section of 2, 8^ at the lowest, being in longitude 

 20-22 \V., and at the greatest 36, being within the meridian of 62-64 

 "SV. 4. Up to longitude 40 the Surface Temperature never descended 

 below oO ; the average lowest of the sixteen meridional sections being 

 51.S8, and the average range 11. 3. 5. In the succeeding fifteen sections, 

 where the lowest temperature was 32, the average lowest was 37.l, and 

 the average range 29. 7. This remarkable 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 



