ST. CROIX RIYER AND PASSAMAQUODDY BAY 



155 



SESSIONAL PAPER No. 38a 



varies witli tlie state of the tide, and with more data it would doubtless throw some 

 light upon the tidal currents. It also appears that the temperature at the bottom at 

 station 3 did not change with the tide, but rose as the season advanced. 



The two isothermal sections of the St. Croix river at the Bioloffical Station 

 (figs. 5 and 6), taken at nearly opposite states of the tide upon succeeding days, show 

 a most interesting change in the arrangement of the layers of water. It will be seen 

 that with a rising tide (fig. 5), the warmer water is massed near the Canadian shore 

 — the right hand side of the figure — while with a falling tide (fig. 6), the colder 

 water is heaped up at almost exactly the same place, while the warmer water is spread 

 out towards the United States bank. 



The section of the river at St. Andrews (fig. 13) shows the same general arrange- 

 ment of the water, showing that it extends down to that point. It also confirms the 

 evidence of a tidal change, as it will be noted that the cold water is about the centre 

 of the river, while the section represents observations taken between flood tide and 

 one-third ebb — just the time when the other two diagrams would lead us to expect 



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Fig 13. — Profile section ot the St. Croix River at St. Andrews, Aug. 

 10. Tide beginning to fall (flood to g ebb). 



the current of cold water to be crossing from the United States to the Canadian 

 bank. This is a most interesting set of facts, which demands further investigation, 

 as our present knowledge of the conditions in the St. Croix river and Passamaquoddy 

 bay suggests no explanation. Apparently the great tidal currents in the bay swing 

 round the current coming down the river, but just what these currents are and how 

 they act we do not at present know. 



It is also noteworthy that the warmest water does not pass through the channel 

 between Navy island and the Canadian shore, the water there being comparatively 

 cold, and the surface there being colder than at any other part of the section. Thus 

 it would appear that while the surface and the bottom water both pass outside Navy 

 island, some of the water from middle depths rises and runs through that channel. 

 It may be that the rising tide has completely filled the narrow channel there with 

 cold water from outside and forces the warmer water in the river to keep to the outer 

 passage, where it flows over the cold water which advances to meet it. 



The section at the "Western passage (fig. IT) shows isotherms which, though more 

 uniform than those in the St. Croix river sections, indicate the same general arrange- 

 ment as that shown with a falling tide. In this section the tide is 'just beginning 

 to rise, and the isotherms, as we would expect, appear to be flattening out and prob- 

 ably rising on the United States side, the left-hand side of the figure. The fact that 



