ST. CROIX RIVER AND PA88AMAQU0DDT BAT 

 SESSIONAL PAPER No. 38a 



153 



From the data recorded a temperature curve for each set of observations at each 

 station was drawn, and from the graphs thus obtained, isothermal sections were 

 comstructed. The isotherms in every case were taken to represent the lowest limif 

 of the temperature marked upon them. 



The graphs show that at different stages of the ebb-tide, there is not much change 

 in the shape of the curve, but in the case of the section of the St. Croix river at the 



^i^-4- 



Fig. 1. — Temperature curves at Station 1 : (a) Aug. 7, \ ebb ; Aug. 6, \ flood ; (c) Aug. 19, \ ebb. 



Fig. 2. — Temperature curves at Station 2 : (a) Aug. 7, \ ebb ; (b) Aug. 4, ebb ; (c) Aug. 6, \ flood ; 

 Aug. 19, § ebb. 



Fig. 3. —Temperature curves at Station 3 : (a) Aug. 5, § ebb ; (b) Aug. 7, \ ebb ; (c) Aug. 6, § flood ; 

 (d) Aug. 4, ebb ; (e) Aug. 19, \ ebb. 



Fig. 4.— Temperature curves at Station 4 : (a) Aug. 6, | flood ; (b) Aug. 5, § ebb; (c) Aug. 8, \ 

 ebb ; (d) Aug. 19, \ flood. 



Biological Station (figs. 1-4), the whole curve moves to the right, i.e., the tempera- 

 ture rises at all depths. The graphs also show that the whole of the water increases 

 in temperature as the summer advances. It will be noted that the temperature falls 

 most rapidly near the surface, as a rule, and in many cases least rapidly about mid- 

 water. The graphs at several stations, however, show that this condition is reversed, 

 the most rapid decrease in temperature occurring in mid-water. This is particularly 

 noticeable at stations 1, 10, 12, 16, 17 and 18 (figs. 1, 12, 10, 22, 11 and 15), while 

 some of the other curves sviggest it. It is a noteworthy ' fact that this character 



