IN THE UNITED KINGDOM AND FKANCE. 75 



tain class of organized beings, I may be permitted to mention that the 

 peculiarities of the climate of Ireland, which arise from its atmosphere 

 deriving a considerable amount of warmth and moisture from the sur- 

 rounding seas, have been referred to in order to explain the existence of 

 a remarkable class of perennial plants found along the western and south- 

 western shores of the island.* The plants in question belong chiefly to 

 the family of heaths, and grow abundantly on the northern coast of 

 Spain, and they are scattered along the east shores of the Bay of Biscay 

 up to some of the localities on the west coast of France, where the obser- 

 vations whose results are given in Table II. had been made. A few of 

 them have been also found very sparingly at the south-western extremity 

 of Cornwall, but not in other portions of Great Britain. Mild and humid 

 winters are the most important conditions required for this flora, and it 

 would be impossible to point to a better illustration of the influence of 

 the comparatively warm sea water beating against the western coast of 

 Ireland, than the existence of these South European plants in a latitude 

 so much to the north of their usual position, as that of the counties of 

 Galway and Mayo. 



The superior temperature of the sea in deep water, as compared to 

 shallow water, in the month of October, is explained by the decrease of 

 sunshine while the action of warm currents continues unabated. On 

 the other hand, the superior temperature of the inshore water during 

 the summer months, as disclosed by Tables I. and II., results from the 

 greater influence of the sun during these months. 



In summer, when the tide retires from shallow bays 3 a large extent 

 of beach becomes frequently exposed to the mid-day sun, and this rapidly 

 absorbs the solar heat. As the water of the incoming tide overflows the 

 heated surface it becomes sensibly warmed, and it may thus exhibit an 

 exceptionally high temperature. The conditions most favourable to this 

 result would arise on bright days in a shallow bay, surrounded by hills 

 on the north and east, and with high water two or three hours after 

 noon. 



The following deductions may be fairly drawn from the facts and 

 reasonings contained in this report : 



1. The temperature of the sea on the coast of Ireland varies within 

 narrower limits than on the coast of Great Britain, or, in other words, it 

 is more equable throughout the year and also during the summer season, 

 when oyster breeding takes place. 



2. The temperature of the sea at noon on the Irish coast, especially 

 on the south and west coasts during the months of June and July is, 

 upon the whole, higher than on the coast of Great Britain, and less than 

 on the west coast of France. 



3. This temperature seems to be sufficient for the requirements of 

 oyster breeding, and therefore, a fortiori, the temperature about two in 

 the afternoon under the conditions above referred to. 



4. The highest temperature of the seas surrounding Ireland, and pro- 

 bably also of those surrounding Great Britain, is during the month of 

 August, and the least during the month of February. 



5. Any advantages as to temperature possessed by the seas which wash 

 the Irish coast are unquestionably due to the thermal influence of currents 

 connected with the Gulf Stream. 



* Proceedings of the Royal Irish Academy for May, 1867, and British Association's 

 Report for 1868, trans, sections, p. 98. 



