ca 
cured in 1888 to 1891, but the increase in the catching power of 
fishing vessels makes comparison difficult. 
The comparatively high values for tidal data in the years 
1912 and 1913 would be followed by the year-classes of 1913 and 
1914, and these have been shown to be the most important amongst 
the older year-classes of our shoals. 
An interesting point with regard to this relation between tidal 
data and herring catches is that Helland-Hansen and Nansen 
found, for the years 1901 to 1905, there was a relation between 
the extent of coastal water and the sprat fishery, whilst Lea con- 
tinuing the investigations, 1910 to 1912, found that this relation 
no longer held. Helland-Hansen and Nansen found the curves 
representing the coastal water area and sprat catches tended to 
run parallel, and Lea that the high sprat catches of 1911 coincided 
with the small extent of coastal water in that year.* 
The periodicity shown above and the finding of two maxima 
for herrings in the nineteen-year period, found by Professor 
Thompson for intertidal range, have indicated the possibility of 
a lunar period of nine years occurring in our herring fishery. 
The quantities of herrings cured on the east and west coast 
of Scotland have been arranged in nine-year periods in Table IIT. 
for the years 1815 to 1920, and the totals for each year of the 
period from 1824 to 1913 are shown graphically in Figure iII. 
Data for Yarmouth catches, sepplied by Mr. Beazor, are similarly 
dealt with from 1869. 
It is possible if in any year herrings are found to be plentiful 
on one coast of Scotland and less abundant on the other that a 
concentration of fishing vessels will intensify the difference in 
catches, and also the gradual improvement in the catching power 
of fishing vessels may tend to make the totals for the later years 
of the period have a high value. 
The curves show some interesting points of agreement and 
difference. In all cases year number 3 is marked by high catches. 
For years number 6, 7 and 8 the west coast curve shows a poor 
fishery, whilst for the same years for the east coast high catches 
are indicated. The Yarmouth catches show a gradual increase 
in catches during years 7, 8 and 9. 

* Hjort. Fluctuations in the Great Fisheries of Northern Europe. Report and Proc. 
Verb., vol., xx., page 191. 
