EXPLANATION OF OCEAN TEMPERATURE CHART No. 18. 



NANTUCKET NEW SOUTH SHOAL LIGHT-SHIP. 

 Ohseivcrs: T. S. James, A. .J. Sandsbuhg, Isaac Hamulkx. 



Location of station. — Nantucket (or Davis') Now South Shoal liglit-ship is placed at the southern oud of Nao tucket 

 Shoals, about 3 miles SSE. of the shoalest part of Davis' New South Shoal, and 21 miles SE. of Nautucket Island, the 

 nearest land. It is distant from Vineyard Sound light-ship about 58 miles in a southeasterly direction. In the im- 

 mediate vicinity the depths range from 11 to 18 fathoms. The water deepens gradually seaward, attaining a depth of 

 10 fathoms at distances of 22 to 25 miles ; the 100-fathoui curve is distant about 60 miles. 



Geo'jrapliical position.— hatilmh; 40° 54' (51") N. ; longitude, (iOo 40' (26") W. 



Dcptli o/ i(ia(tr.— Sixteen to IS fathoms. 



liange of temperature (12 months).— Air, 4:!'=' (^2iP to 69^) ; surface, 28°. 5 (:W.5 to 62°). 



Tlie position of this light-ship, over 20 miles from the uearest land, and in the course of those schools of surface 

 lish that pass around or through the Nantucket Shoals In their migrations, especially fits it as a permanent station 

 tor teuipei-ature and otlur observations bearing upon the coast fisheries. The temperature of the surface water is 

 more equable here than at any of the preceding stations north of the Florida Reefs, but the maximum surface tem- 

 perature at Nantucket New South Shoal is 8° lower than the minimum at Fowcy Rocks. The comparatively slight 

 range of temperature throughout the year has made it possFldc to utilize tlie winter temperatures, all of which have 

 been i>lot(ed on the chart. 



The range of air temperature from Mari'h 1 to .January I is 40° (29° to 09°), nearly the same as at Vineyard Sound 

 lightship, the maximum being 21° lower at New South Shoal than at Vineyard Sound. The lowest air records for 

 the winter months also differ only 2° at these two stations. The maximum surface temperature at New South Shoal 

 is, however, G° lower tliaii at Vineyard Sound, and the miuimum between JIarch and .January, about 3° higher. The 

 r.iuge of surface temperature is, therefore, considerably less at New South Shoal. 



Tdlile .fli0!vi"ij the direction of the wind, hij quadrants, for each month of the year, being the ntrans of five years' ohsenalions. 



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