436 report*7T^^ >MMissioyER of fish and fisheries. 



II. 9. — FREE SWIMMING AND SURFACE ANIMALS. 



Uiuler this head I have included all the animals found swimming tree, 

 whethei' in the bays and sounds, or in the colder region outside. Nor 

 liave I, in this case, attempted to separate those of the estuaries and 

 other brackish waters, although such a distinction might be useful had 

 •we sufficient data to make it even tolerably complete. But hitherto 

 very little surface-collecting has been done in waters that are really 

 brackish ; and, moreover, since every tide must bring in myriads of free- 

 swimming creatures with the waters from outside, it will always be dififi- 

 calt to distinguish between those that are thus transported and those 

 that i^roperly belong to the brackish waters. A distinction between the 

 free-swimming animals of the bays or sounds and those of the open 

 coast has not been made, partly on account of the constant intermixture 

 of the waters and their inhabitants by the tides, and partly because the 

 observations that were'made do not indicate any marked difference in 

 the life or in the average temperature of the surface waters, though the 

 waters of the shallow bays become more higlil^^ heated by the direct 

 heat of the sun in summer. The waters of the open coast are evidently 

 more or less warmed by the Gulf Stream, and in fact numerous species 

 of animals that properly. belong to the fauna of the Gulf Stream are 

 constantly brought into Vineyard and Nantucket Sounds by the cur- 

 rents, showing .conclusively that a portion of the Gulf Stream water 

 must also take the same course. 



In Vineyard Sound, during August and the first part of September, 

 the temperature of the surface water in the middle of the day was gen- 

 erally from 68° to 71° Fahrenheit ; September 9, off Tarpaulin Cove, 

 the surface temperature was 00°; off to the west of Gay Head, in mid- 

 channel, it was 07° Fahrenheit; but farther out, off No Man's Land, on 

 the same day, it was 62°, (bottom, in 18 fathoms, 02J° ;) a short distance 

 west of No Man's Land it was 63°, (bottom, in 11 fathoms, 59°;) about 

 sixteen miles off Newport, at the 29-fathom locality, it was 62° on Sep- 

 tember 11, (at the bottom 59°;) off Cuttyhunk, in 25 fathoms, it was 

 64° at the surface on September 13, (bottom 62i°.) According to the 

 record made by Captain B. J. Edwards, during the past winter, from 

 observations taken at 9 a. m. every morning, at the end of the Govern- 

 ment wharf at Wood's Hole, (where the temperature must be nearly 

 identical with that of Vineyard Sound,) the average temperature of the 

 surface water was 31° Fahrenheit, from December 27 to February 28. 

 The average temperature for that hour during January was 31.42° ; 

 the lowest was 29° on January 29, with the wind N. W. ; the highest 

 was 38° on January 17, with the wind S. W. ; on the 18th, 19th, and 

 22d it was 35°. The average for February was 30.75° ; the coldest was 

 29°, on February 24 and 25 ; the highest 33°, on February 8, 17, and 

 19. The temperature at the bottom (at the depth of nine feet) was 

 also taken, but rarely differed more than one degree from that of the 



