8 Fishery Board for Scotland. 



figure (Fig. 1a), we have, in the first place, the uneven line which is 

 directly drawn from our data of Mean Temperature — relating, in 

 this particular case, to a strip across the Atlantic, east and west, 

 between lat. 40° and lat. 42° N. Superimposed upon it is a smooth 

 curve, which must approximately represent that actual variation in 

 temperature, which the recorded numbers and broken line express 

 not very accurately, but as nearly as whole numbers can. In short, 

 the drawing of this smooth curve tends to bring out of our recorded 



70 



65 



60 



55 



? 70 V 



50 F 



IOC. 



Fig. 1a. — Mean siirface-temperature in the North Atlantic, on the parallel of 



41° N. lat. 



data a little more than they obviously, but not more than they 

 implicitly, contain. Lastly, from the smooth curve, we can now 

 read off the position of the isotherms, that is to say, the points in 

 latitude where the curve crosses the ordinates indicating 50°, 55°, 

 or 60° Fahrenheit as the case may be. Moreover, it is obvious 

 that, by using another scale of temperature, we may, without 

 redrawing our curve, read off" the position of our isotherms according 

 to degrees Centigrade, or any other temperature scale we please. 

 The result of the whole process is shown in the annexed Table. 



(1) Means of observed Atlantic Surface-temperatures, between 

 Lat. 40° and 42° N. 



f70° 68° 66° 64° 62° 60° 58° 56° 54° 52° 50° 48° 46° 



(68° 66° 64° 62° 60° 58° 56° 54° 52° 50° 48° 46° 44° 



51-4 52-8 57-2 60-1 62-2 64-0 64-3 64-0 63-1 62-5 61-5 62-6 65-1 



/44° 42° 40° 38° 36° 34° 32° 30° 28° 26° 24° 22° 20° 



(42° 40° 38° 36° 34° 32° 30° 28° 26° 24° 22° 20° 18° 



65-7 65-2 65-2 65-2 64-9 64-4 64-2 63-6 63-2 63-2 62-8 62-2 62-1 

 ri8° 16° 14° 12° 10° 

 (16° 14° 12° 10° 8° 



Long. W. 

 Temp. F. 

 Long. W. 

 Temp. F. 

 Long. W. 

 Temp. F. . 62-1 61-8 61-7 61-1 60-2 



(2) Temperatures interpolated from the above data, along the parallel of 41° N. 



Long. W. . 70° 65° 60° 55° 50° 45° 40° 35° 30° 25° 20° 15° 10° (5°) 

 Temp. F.. bV\ 557 63-4 64-0 62-2 64-8 65-2 64-7 63-9 63-0 62-2 61-9 60-7 (68-7) 



