466 HARSHBERGER— INFLUENCE OF SEA WATER [April 22. 



dig deep holes in the tough resisting marsh sod. The water for 

 study was dipped either directly from holes in the marsh or taken 

 from the ocean and open bays along the New Jersey coast. The hole 

 was dug in all cases deep enough to allow the soil water to perco- 

 late into it, and upon this water the specific gravity readings were 

 made. The region especially traversed in this way extended from 

 INIanasquan Inlet on the south to Sandy Hook Bay on the north, and 

 thus an insight was obtained of the problems concerned in the distri- 

 bution of the various species of salt marsh plants. 



Field Observations and Data. 



Altogether sixty readings were made with the first style of sali- 

 nometer used. This tvpe had such a small range of scale divisions 

 that it was discarded as being too inaccurate for the purposes of the 

 salt marsh investigation where the total salt content of the water 

 increased, or decreased, by almost inappreciable amounts. Although 

 manv of these observations are of interest, they are not incorporated 

 here. The second style of In^irometer was like the final one adopted, 

 as to the divisions of the scale, but it lacked a thermometer. The 

 data obtained by this hydrometer are considered here, but they are 

 onlv of comparative value, because they lack the accuracy of the 

 later readings which were made for both specific gravity and tem- 

 perature. They are of value because they give habitat relationships 

 not included in the more accurate data obtained later. 



For the above reasons the field observations will be considered 

 under two heads : ( i ) the readings made by the hydrometer without 

 the thermometer, and (2) the readings which include both hydro- 

 metric and thcrmometric measurements. 



Hydronictric Readings zcithont Thcnnoiiictcr. — The readings 

 which are numbered consecutively from 1-70 inclusive are arranged 

 geographically as afl:"ording more interesting comparative data. They 

 stand as follows : Beginning in the north readings were obtained 

 along the Shrewsbury River, starting at the railroad bridge connect- 

 ing Highland Beach with the Navesink Highlands proper. Plum 

 Island, where the first measurements were made, is a small island 

 back of the Sandy Hook peninsuula in Sandy Hook Bay. Undoubt- 



