ON THE SEASONAL VARIATIONS OF TEMPERATURE. 



467 



vations on tlie water of the sea at certain fixed stations is given. The 

 summarised results in tabular form are given below, in order to render 

 them more available to other workers, and to afford ready compari- 

 son with other records carried on simultaneously in different places. 

 The following tables are expressed in Centigrade degrees, most of the 

 instruments used by the Board's observers being graduated on that 

 system. 



Ardrishaig and Brodick are situated on the Clyde Sea Area, and 

 observations of surface-water only are taken twice daily at the end of the 

 steamboat piers in water never less than G feet deep at low water. 



The Bell Rock Lighthouse stands in the North Sea nearly opposite 

 the estuary of the Tay and twelve miles south-east of Arbroath, being 

 thus quite beyond land influence. 



Monthly Mean Temperatures of the Sea. 



Oxcar Lighthouse is situated in the Firth of Forth a little to the west 

 of Aberdour, and is built on a rock surrounded by deep water. From its 

 situation it is much under the influence of fresh water carried down by 

 the Forth and its small tributary the Almond, when in flood. The tide 

 here has considerable power, and the observations were sorted out in order 

 to detect any tidal disturbance. As the two daily observations were taken 

 six hours apart, they were almost exactly at opposite phases of the tide. 

 Neglecting all cases except those in which the observations were within 

 an hour and a half of high or of low water the results were classified as 

 given in the table on next page. 



The North Carr Rock Light-vessel is anchored off Fife Ness, just 

 beyond the mouth of the Firth of Forth, in 24 fathoms of water. The 

 situation is a very exposed one and little subject to land influence. Tbf^ 

 monthly means at this station and their tidal discussion are on pp. 468, 

 469. The surface-temperatures recorded are probably too low on account 

 of the time which was allowed to elapse between raising the thermometer 

 from the water and reading it, and of the exposure of the wet bulb to 

 the air. 



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