EXPLANATION OF OCEAN TEMPERATURE CHART No. 18. 



NANTUCKET NEW SOUTH SHOAL LIGHT-SHIP. 

 Obse:vers: T. S. James, A. J. Sandsburg, Isaac Hamblex. 



Locdlion of station, — Nantucket (or Davis') New South Shoal light-ship is placed at the southern end of Nantucket 

 Shoals, ahout 3 miles SSE. of the shoalest part of Davis' Now South Shoal, and 21 miles SE. of Nantucket Island, the 

 nearest land. It is distant from Vineyard Soand 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 

 !0 fathoms at distances of 22 to 25 miles ; the 100-fatbom curve is distant about 60 miles. 



Geographical position.— 'L&titade, 40° 54' (51") N. ; longitude, 69° 49' (26") W. 



Depth of water. — Sixteen to 18 fathoms. 



Bange of temperature (12 months).— Air, 43° (20° to C9°) ; surface, 28°. 5 (33"^ .5 to 62°). 



The position of this light-ship, over 20 miles from ihe nearest land, and in the course of those schools of surface 

 liHh that pass around or through the Nantucket Shoals in their migrations, especially fits it as a permanent station ' 

 tor temperature and other 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 Fowey Eocks. The comparatively slight 

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

 Ix-en plotted on the chart. 



The range of air temperature from March 1 to January 1 is 40° (29° to 69°), nearly the same as at Vineyard Sound 

 light-ship, the maximum being 3i° 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, 6° lower than at Vineyard Sound, and the minimum between March and January, about 3° higher. The 

 range of surface temperature is, therefore, cousiderably less at New South Shoal. 



Taile showiug the direclion of the wind, T)i/ quadrants, for each month of the year, being the means of five years' observations. 



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