130 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Bahama Bank Ship and Carnarvon Bay Ship I consider to 

 " open-sea " stations, which are much less under the influence 

 of the land than is Morecambe Bay Lightship. This is about 

 16 miles distant from the mouth of Morecambe Bay, and the run 

 of the tidal streams is such as to transport water from the 

 Bay to the region between the Bahama Bank and the More- 

 came Bay light vessels. Therefore, the sea-region about the 

 latter position has a greater range of temperature than at 

 either Bahama Bank or at the middle of Carnarvon Bay. 

 It is to the influence of the land that we look for the explanation 

 of this greater range. Now the greatest differences of tem- 

 perature between sea and land are experienced during the 

 months January fco March and June to September, and so we 

 find it advantageous to use either or both of these periods in 

 making comparisons between the various stations. 



Two temperature readings are taken each day at the light 

 vessels — at sunrise and at 4 p.m. It is the latter readings 

 that are taken into consideration here : the fact that they 

 are made at continually varying states of the tide is a condition 

 that may be neglected, as we shall see later. The readings 

 are Fahrenheit ones, but they have been converted into the 

 corresponding Centigrade values. 



The daily temperatures for the months January to March 

 are grouped in periods of ten days, and means are calculated. 

 These means are then plotted at the centres of the periods : 

 thus, the mean for January Ist-lOth, 1907, is 6-27° C, and 

 this figure is plotted against January 5th. The ten-daily 

 points are then found, and a smoothly-running curve is drawn 

 through or among them. Mean temperatures for any day 

 are found from this curve. 



If these smoothed curves are drawn for the first three 

 months of each of the years considerable differences will be 

 found. Thus, in January-March, 1912, there is a comparatively 

 great range, which is about 7° C. at the beginning of January 



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