SEA-FISHERIES LABORATORY. 229 



in one case 2'83° C. lower than that of the surface, and in 

 all four cases over 1° in ammmt. But the July cruise, 

 some six weeks later, disclosed very different conditions, 

 for the mean difference then was less than 0'3° C. This 

 cruise was made after a week of rather exceptional 

 weather, when the wind had been blowing at times with 

 the force of a gale, the result being that the water over 

 the whole area investigated had become mixed up, 

 practically obliterating the differences previously 

 existing. This effect of a storm in relatively shallow 

 water has been pointed out by Kriimmel,* in the case of 

 the Baltic Station " D Ostsee 7," where, after an interval 

 of two days of stormy weather, the temperatiire difference 

 between surface and bottom had practically been reversed, 

 the mean remaining about the same. In the Irish Sea, 

 then, a spell of calm, warm weather leads to the heating 

 of the surface layers and the establishment of a condition 

 of spurious stratification. Significant vertical tempera- 

 tures are not to be detected anywhere between Britain and 

 Ireland, as is shown by the numerous soundings made all 

 down the Channel by the " Helga "'in 1909. Only in the 

 stations South from the Tuskar were such disclosed. At 

 the Irish station, 51° 55 / N, 6° 49' W, there was a 

 difference of nearly 5° C. at a depth of 64 m. and at 51° 

 22' N., 7° 0' W., a difference of 8-2° C. at a depth of 119 m. 

 This was in August. The soundings, during the same 

 cruise, in ' the fairway of the Channel between Mull of 

 Galloway and the Tuskar showed differences of just the 

 same order as those we found between Calf of Man and 

 Holyhead at about the same time. 



The Surface Temperatures in 1909. 



At the minimum; mean date, February 15th, 1909. 



The surface temperatures are represented by the sketch 



* Beteilig. DeutscJilands a. d. Internal. Me&resforsch. Ill Jahresber. 

 Berlin, 1906, p. 19. 



