72 APPENDIX TO ItEPORT ON OYSTER CULTURE 



Academy. The Rev. Provost H. Lloyd has given the results regarding 

 sea temperature in a memoir published in the Transactions of the 

 Academy, and from these and other facts, to be presently quoted, ] 

 have been led to lay down the approximate annual isothermal lines for 

 the water around the Irish coast. The most remarkable result estab- 

 lished by these observations is, that the mean temperature of the ocean 

 which washes the coast of Ireland surpasses the mean temperature of 

 the air over the island, and I was thus led to rigorously deduce the 

 general law that the representation of temperature distributing in Ire- 

 land must be made by isothermal lines, or lines of equal temperature, 

 many of which must be re-entrant curves within the island. I subse- 

 quently extended the same conclusion to Great Britain, and showed 

 that it was verified by the results of meteorological observations.* The 

 red lines on the map which accompanies this report, show the distribu- 

 tion of temperature over the surface of Ireland in conformity with my 

 deductions and with observation. 



Mr. Nicholas Whitley has made a series of observations on the tem- 

 perature of the sea on the coast of Cornwall, from which conclusions 

 similar to those deduced from the Irish observations may be drawn. 

 All of these results confirm the generally admitted opinion, that the 

 coasts of the British Isles are bathed by water which has acquired a 

 considerable amount of warmth from currents which are offshoots of the 

 Gulf Stream. This great current splits into branches between the 

 Azores and Newfoundland, and these branches carry their thermal 

 influence to the western and northern coasts of Europe. The maximum 

 temperature of the stream, as deduced from the most recent observa- 

 tions, is 88° within the Gulf of Mexico itself; it is 84° opposite Char- 

 leston, and moves with a velocity of from seventy to eighty miles per 

 day. The line of demarcation between the stream and the cold water 

 on the shores of America is well denned, so that, for instance, in May, 

 1851, on board the Nile, between Bermuda and Halifax, the water under 

 the ship's stern was at 70°, while at the same moment, under the bow, 

 the thermometer stood at 40°. This was on the N.N.W. edge of the 

 stream. This sharpness of definition is gradually lost as the current 

 approaches Europe, and its temperature also falls while its surface 

 extends. Nevertheless, the offshoots emanating from it retain sufficient 

 warmth to make its influence felt as far as the North Cape and Spitz- 

 bergen. Thus, at the North Cape, in latitude 71° 11', the sea remains 

 open all the year round, while in the Baltic the water is frequently 

 frozen for many months. The warmth possessed by the waters bathing 

 the coast of Ireland gives to it a representative character in physical 

 geography, as exhibiting one of the best defined examples of an insular 

 climate on the surface of the globe. This is in part a result arising 

 from the superiority of water, as an agent for absorbing, retaining, and 

 distributing solar heat, compared to the other materials of the earth's 

 coating, as I pointed out several years since, f and which is now becom- 

 ing very generally acknowledged by those who pay attention to the 

 climatology of the globe. The effect of land under sunshine is to rapidly 

 throw off' the heat it receives into the upper regions of the atmosphere 

 and the interplanetary spaces, both by day and night, and thus, although 

 it causes a considerable increase of temperature in the stratum of air 

 over it by day, it is not well adapted for storing up and retaining heat. 



* "The Atlantis," vol. I., p. 396. "Philosophical Magazine," October, 1858, and 

 "Proceedings of the Royal Society" for June, 1858. 



f " Atlantis," vol. II., January, 1859. "American Journal of Science," May, 1859. 

 '* Phil. Mag.." vol. XVII., 4th Series. 



