284 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Stations 5, 6, and 7 for the years 1907-1912. The 

 difference between the various years with respect to the 

 annual temperature range is considerable : thus the 

 range in 1909 is only 476°, while that of 1911 is 7-91°, 

 or 8'29° if we compare August of 1911 with February 

 of 1912. This difference is much greater than any that 

 can be accounted for by "accidental" variations of 

 surface temperature, or interchange of water between 

 surface and bottom, or errors due to observation, or 

 variation in the dates of the quarterly cruises. There 

 seems to be no doubt that it must be traced to events 

 occurring outside the Irish Sea, that is, to variations 

 from year to year in the temperature of the water entering 

 this sea area. This variability in annual temperature 

 range is, at present, all that can safely be deduced from 

 the data : the form of the curve does indeed suggest a 

 periodicity in these variations, a periodicity which is 

 exhibited best perhaps in the amplitude of the annual 

 temperature wave, and in the value of the figures for 

 the " mean " months — May and November. But, 

 obviously, the period of years throughout which the 

 observations have been carried on is too small to allow 

 of the deduction of conclusions of this kind. 



II. — Temperature Differences in the Eastern Side of the 

 Irish Sea. 



Even in this very limited sea-area these differences 

 are fairly considerable, and this is because there are two 

 main series of conditions : (1) The effect of the very 

 extensive sand-banks fringing the coasts of Lancashire 

 and Cheshire, and tending to produce great temperature 

 differences; and (2) the effect of the relatively strong 

 inflow of water round Anglesey from the open Channel : 

 this tends to reduce temperature differences, in the regions 



