600 



BULLETIN OF THE BUREAU OP FISHERIES 



The fact that the deep water is warmer in the Bay of Fundy, and for that 

 matter in the northeastern part of the gulf generally, than in the southwestern, while 

 the surface is so much colder, deserves special emphasis because of its bearing on 

 the circulation of the two regions (p. 924) . 



In St. Marys Bay the relative difference between surface and bottom temper- 

 ature increases from the mouth, inward, in July, as follows, if the total depth of 

 water be taken into consideration. 



Surface and bottom temperatures at successive localities from the mouth of St. Marys Bay toward Us 

 head, July, 1915. {From Craigie and Chase, 1918.) 



The water is likewise kept comparatively homogeneous in temperature out to the 

 100-meter contour over the coastal banks off western Nova Scotia by active tidal 

 stirring throughout the summer. Dawson (1905, p. 15) has already called attention 

 to the thermal effect of vertical circulation in this region, where the topography of 

 the bottom causes "a long trail or wake of colder water to extend from islands or 

 shoals along the line of the current; as, for example, north and south from Lurcher 

 Shoal." He also points out that "when the islands and shoals are numerous, the 

 general effect of these strong currents is to chill the water in the vicinity of the coast 

 by mixing the surface water with the colder water from below." As the result of 

 local disturbances of this sort, the vertical range of temperature is much narrower 

 along the 100-meter contour off Lurcher Shoal in August than at corresponding loca- 

 tions over the western slope of the guK. The temperature on German Bank has 

 proved almost perfectly homogeneous from smiace to bottom in August and Septem- 

 ber, as follows: 



German Bank approximate temperatures 



Deptb, meters 



Sept. 2, 

 1915, 



station 

 10311 



0. 



20 

 40 

 60 



9.44 

 10.30 

 10.20 

 10. 10 



