MADE ON THE COASTS OF EUROPE AND AMERICA IN JUNE 1835. 299 
the intervening spaces, as may be seen by reference to the chart ; and I have therefore 
adopted it as the best approximation I can now obtain to the form of these lines. 
This theory is, indeed, nothing more than a representation of the facts of the case ; 
yet it gives a view of the mechanism of the tides of the German Ocean different from 
any which has hitherto been suggested. The southern rotatory system, which exists 
between the coast of Suffolk and the Netherlands, may be conceived to be kept in 
constant circulation by impulses received from the adjacent tides, that is, an impulse 
at 6 h on the coast of Norfolk, and an impulse at 12 h on the coast of Belgium. Thus 
if resembles a watch or clock, which is kept in continual motion by a sustaining force 
applied at intervals. The larger rotatory system, lying between the east coast of 
Scotland and England, and the coast of Germany and Denmark, does not, like the 
other, return into itself. We may conceive that in this case the tide-wave is turned 
aside by the opposing coast of Norfolk and Germany, so as to be thrown back upon 
itself in the neighbourhood of the coasts of Jutland after an interval of six hours. 
This would explain the vanishing of the tide in that region ; for a tide at 1 2 h com- 
bined with a tide at 6 h are equivalent to no tide at all ; the high water of the one 
filling up the low water of the other. 
19. Besides this completion of our view of the tides of the German Ocean, our 
new materials give us the course of the tide-wave on the coast of Norway, which I 
had not previously ascertained. It appears that the 9 h cotidal line, which must pass 
somewhere near the Orkneys, also touches the opposite coast of Norway at Stavanger 
andTananger ; and as we find the hours go on to 12 k , both in proceeding southwards 
to Cromarty on the one coast and to the Naze on the other, we appear to be entitled 
to conclude that the 9 h , 10 h , and ll h lines extend across the ocean here. But Sta- 
vanger is a point of divergence from which the tide also travels northwards ; for it is 
9 h 43 m at Bergen, 10 b 4 m at Christiansund, ll h 22 m at Andaenes in the Lofoden 
Isles, and l h 30 m at Tromsoe, in latitude 69° 38'. We may judge the 2 h line to be 
not far from the North Cape. And we have thus a tolerably complete view of the 
cotidal lines of the European seas. 
We may observe that here also the tides of islands appear to be later than those 
of the surrounding seas, so as to compel us to make the cotidal lines form loops and 
rings. The tide-hour at Lerwick, on the east coast of Shetland, is 10 b 41 m , though the 
islands appear to lie between the 6 h and 9 h lines. 
Sect. IV. Height of the Tide. 
20. The range of the tide, that is, the height of high water above low water, is very 
different at different places, and is affected by circumstances which it is very difficult 
to analyse. It is, however, clear, that the configuration of the coast exercises a very 
considerable influence upon the amount of this range. Thus the range is very much 
increased in deep inbends of the shore which are open in the direction of the tide- 
wave, as the Bristol Channel and the Gulf of Avranches ; and much diminished at 
2 q 2 
