SEA-FISHERIES LABORATORY. 265 



warm days in February or March, would quickly affect 

 the water at Stat. Ill, and similarly a sudden fall in 

 April, reversing these conditions. The great rise that 

 has been referred to above and also its effect on the 

 vertical distribution of temperatures can be traced quite 

 easily to the weather conditions. After a prolonged 

 period of cold weather with .a steady thermometer, there 

 followed three or four abnormally fine and hot days (the 

 temperature of the air only reached that attained at that 

 time on about five days between then and July 16th). 

 From the 6th to the 9th the sea was calm, there was 

 practically no wind, and continuous sunshine prevailed 

 during the day. The result was a very considerable 

 heating of surface water, the deeper water, however, 

 remaining unaffected. The minor increase on the 15th 

 was due to a similar though less marked cause. 



Vertical Distribution of Temperature. 



These records, though taken in shallow waters, with 

 the exception of one series made in water of over 60 faths., 

 are not without interest, and seem to support the view 

 that the Irish Sea is practically a homothermic water 

 mass, though Johnstoue states that in 60 cases the bottom 

 water was coldest, in three cases was warmest, and in 

 three cases was the same as the surface. 



My records are as follows : — From April 8th onwards 

 10 series were taken at Stat. I, 9 series at Stat. Ill, and 

 1 at Stat. A in deep water. In every case the bottom water 

 was colder than the surface water, but by very small 

 amounts. In all cases but four the difference between 

 surface and bottom water was less than half a degree. 

 These four cases occurred on the 8th and 9th of April. 

 The differences between surface and bottom were 0*90° C, 

 0-75° C, 2-42° C, and 0'.3;;° C. The greatest of these 

 differences is less than those observed by Drew on the 



