CANADIAN FISHERIES EXPEDITION, 191/f-15 227 



cated by plates II and III. Not until the very outermost stations are reached, how- 

 ever, do we encounter true Atlantic water of over 35 per cent salinity. 



Plates IV and V show the distribution of temperature during the spring and 

 summer cruises. Particularly noteworthy is the enormous intermediate layer of tem- 

 peratures below zero, which fills the whole of the gulf of St. Lawrence and a great part 

 of the coastal zones outside. During the spring, it also extends far down towards the 

 coast of Nova Scotia, but in summer the extent is somewhat less. Both above and 

 below this intermediate cold layer, the temperature increases. During summer, we find a 

 surface layer of comparatively high temperature. At the outermost stations, the warm 

 Atlantic water is found. 



The distribution of temperature and salinity, and the hydrographical conditions 

 generally, have been thoroughly dealt with by Mr. Paul Bjerkan,i to whose work on 

 the subject the reader is referred. 



Given salinity and temperature, we can, by means of Martin Knudsen's tables, 

 calculate at and the specific volume; i.e., the volume in ccm. of a gramme of water. 

 If we designate the specific gravity of the sea-water by p and the specific volume by 

 V then we have 



v=-^- (2) 



P 



If, for instance, o=28,16, then p^l- 02816, whence, according to formula (2), v= 

 0-97261. As, however, nearly all the values for specific volume within our area of 

 investigation begin with 0-97, we may simplify matters by omitting this figure and 

 multiplying the remainder by 10^, whereby the specific volumes appear as whole num- 

 bers of three figures, and are thus far easier to manipulate. This is the more permis- 

 sible, since we shall in the following only have occasion to reckon with differences of 

 specific volume. Instead of v = 0-97261, then, we write vi = 261, the equation indicat- 

 ing that a gramme of the water in question represents a cubic capacity of 0-97261 ccm. 



In table 1, the first column shows the depths in metres at the points where water 

 samples were taken, and the second column vi for the samples in question, calculated 

 according to the method indicated above, from the last column in Bjerkan's hydro- 

 graphical table. Plates VI and VII show the distribution of specific volume within 

 the area investigated. It is greatest at the surface, decreasing downwards, which 

 naturally means, that the lightest water lies uppermost, and the heaviest at the bottom. 

 In the Gaspe current and the southern portion of the gulf of St. Lawrence, the specific 

 volume is particularly great. The lines for like values of specific volume, the so-called 

 isosteres, exhibit a far more horizontal and regular course than the isohalines and 

 isotherms. In the upper water layers, the specific volume decreases rapidly with increas- 

 ing depth, especially during summer, wheia the surface water is warmed by the sun ; in 

 the lower strata, however, the decrease takes plac€ far more slowly. 



Plates VIII and IX present a more detailed view of the course of these isosteres. 

 Per the deeper water layers, they have been drawn for each tenth unit of v, in the upper 

 strata for each fiftieth. For general convenience of reading the isostere vi = 500 is 

 here prominently shown. 



1 Paul Bjerkan : Results of the hydrographical observations made in the Canadian Atlantic 

 waters by Dr. Johan Hjort during the spring and summer of 1915. 



