38 BULLETIN OF THE BUREAU OF FISHERIES. 



The resulting narrowness of the littoral (intertidal) zone is a characteristic feature of 

 the region, and stands in decided contrast to the conditions encountered on the Maine 

 coast, where the average tidal range is not less than lo feet. 



4. TEMPERATURE. 



The surface and bottom temperatures were recorded for each of the regular dredging 

 stations of the Fish Hawk and were entered in the original records for these. It became 

 evident, however, that the methods then employed were not sufficiently accurate for 

 purposes of careful comparison ; likewise that the temperature determinations should be 

 taken as nearly simultaneously as possible throughout the entire area under considera- 

 tion. Accordingly, new observations were made at four different seasons of the year, 

 with standardized instruments and in accordance with more precise methods. Density 

 determinations were made at the same time as those upon temperature, but a discussion 

 of these will be deferred till the following section. 



The methods pursued in making the temperature obser^'ations were as follows: 

 Certain stations were selected which were believed to be representative of all sorts of 

 conditions as to geographical position, depth, tidal influences, etc. These were commonly 

 selected from among the regular dredging stations plotted upon the distribution charts, 

 but they were not located by the vessel with any close approach to accuracy. In a few 

 cases, however, other points were chosen, so that it was thought best to give a new set 

 of numbers, or rather letters, to the temperature stations. They ranged from A to Y 

 in the Sound and from A to V in the Bay." (See chart 211.) In taking the August 

 series of temperatures the Fish Hawk was employed; in November and June the 

 Phalarope was used; in March the Blue Wing. The bottom temperatures were obtained 

 with Negretti-Zambra thermometers, provided with the Tanner inverting case (Tanner, 

 1884, p. 26); and the instrument was in all cases left at the bottom for a period of 10 

 minutes. Our own and previous tests (see Kidder, 1887, p. 203) have shown that reliable 

 results can not be obtained in less time. The thermometer was then upset by a 

 "messenger," rendering impossible any further change in the column of mercury, except 

 the slight expansion or contraction of the thread itself, which could be allowed for 

 whenever the water and air temperature differed sufficiently. The surface temperature 

 was taken by means of an ordinary thermometer of the Queen or Tagliabue make, 

 having a long scale. Surface water was drawn in a dip bucket and kept in the shade 

 while the thermometer w-as in use. When air and water temperature differed much, 

 the pail of water was changed at least once before the final reading was made. The 

 air temperature was likewise recorded, though this was far from exact, owing to the 

 artificial sources of heat necessarily present on a steam vessel. 



August series. — The first series of temperature determinations was made between 

 August 14 and 29, 1907. Twenty-five observations in Vineyard Sound were made 

 on August 14, 15, and 16. The order followed was such that stations scattered 

 throughout nearly the whole length of the Sound were visited on the same day. Thus, 

 differences due to locality would not be confused with differences due to meteorological 

 changes. Buzzards Bay was then covered on August 19 and 20, most of the stations 

 being reached on the first day. Certain stations in Vineyard Sound were also revisited 



o Not all of these stations were included in every series of observations, while the greater number of the Bay stations were 

 omitted from the March series. 



