EXPLANATION OP OCEAN TEMPERATURE CHART No. 19. 



POLLOCK RIP LIGHT-SHIP, MASSACHUSETTS. 

 Observers: William Haffaeds, James F. Kelly, Joseph Allen, Jr. 



Localion of stallon. —Th\s light-sbip is located in the northeastern entrance to Nantucket or Vineyard Sound, and 

 3} miles SE. by E. i E. from Monomdy Point light-house, at the southeastern extremity of Cape Cod. It is IJ miles 

 distant from Pollock Rip Shoal proper, which lies between it and Monomoy Island, and is surrounded on nearly all 

 sides, at different distances, by small shoals or groups of shoals. There is, however, no land to the northeast, east, or 

 southeast of it. It is anchored in a depth of 5 fathoms, and the depths about it range from 4 to 7 fathoms. The bot- 

 tom in this region consists of sand and gravel. Nantucket New South Shoal light-ship is about 36 miles nearly south. 



Geograjihical position.— La,litnde, 41° 32' (27") N. ; longitude, 69° 5.5' (15") W. 



Depth of irater. — Five to 7 fathoms. 



Sange of temperature (March 1 to January ]).— Air, 39° (27° to 6t)°); surface, 30°.5 (32° to 62° -5). 



The curves of surface temperature are more irregular and less uniform than at the three or four preceding stations, 

 and in many cases the variations do not appear to be due to the influence of the air. They may be caused in part by 

 the currents flowing through the numerous passageways between the surrounding shoals. The ranges of temperature 

 correspond closely with the same at Nantucket New South Shoal, the maximum air temperature being 3° lower at this 

 station, but the maximum and minimum for the surface are almost precisely alike at both. The maximum surface 

 temperature at Pollock Rip, located at the eastern entrance to Vineyard Sound, is 5|° lower than at Viueyard Sound 

 light-ship, at the southwestern entrance to the same body of water. 



Tahle showing the direction of the winds, ig quadrants, fur each month of the year, heliig the nuans of five years' observations. 



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