712 Proceedings of the Royal Irish Academy. 



Great Britain and Ireland ; but the maps constructed from these facts 

 are much less valuable owing to the arbitrary deformation of the facts 

 by the so-called correction for height. I have grouped the tempera- 

 ture results with others which are published in some of my Papers, 

 and these being the true representations of the actual state of things, 

 serve better to construct the temperature map which accompanies this 

 Paper. 



Mr. Buchan would have done well if he had profited by the sugges- 

 tion of his correspondent, Dr. von Wojeike, who wrote: " I believe the 

 best attempt to trace the isotherms for a great part of the globe was 

 made by Petermann in his Mitheilungen, vol. vi., because he does give 

 the actual facts, and, what is extremely important, for great continents 

 he does not reduce to the sea levelP 



That the isothermals of the islands of Great Britain and Ireland 

 must conform to the law I have enunciated is certain from the 

 acknowledged excess of temperature of the seas bathing their coasts. 

 Mr. "Whitley has made a series of observations of the temperature of 

 the sea off Cornwall, which prove that the sea is from 2° to 3° warmer 

 off the south-west coast of England than the air. Prom Mr. Buchan's 

 Papers it seems that the mean sea temperature surrounding the north 

 and north-east coasts of Scotland is 48°, and at the Orkney, Shetland, 

 and "Western Isles, the temperature of the sea exceeds that of the air 

 by 3°. In my Report on the Temperature of the Sea on the Coasts of 

 Great Britain and Ireland, appended to the Report of the Royal Com- 

 mission on Oyster Culture, I have given results of observations which 

 show that the sea temperature around the coast of Ireland is in general 

 superior to that of the air, and that the same superiority holds good 

 for the greater part of the coasts of England and Scotland. On the 

 east coast of Ireland, in Dublin Bay, on a day in mid- winter, with the 

 ground still slightly frozen, I have plunged a thermometer into the 

 sea water, and the mercury immediately rose to 41°, while a ther- 

 mometer hanging freely in the air stood at 36°. At other seasons of 

 the year the difference would be less, and in the months of greatest 

 sunshine — May, June, and July — the result might be slightly reversed, 

 as appears from facts I have published in the Report above quoted.^ 



The temperature map constructed from the more extended obser- 

 vations recorded in the foregoing Tables shows that the isothermal lines 

 of Great Britain and Ireland conform to the law cited at the com- 

 mencement of this Paper, and the influence of distance from the sea 

 is manifest in consulting the column of distances and comparing them 

 with latitudes and temperatures. As long as the shores of these 

 islands continue to be washed by the heat-bearing currents of the 

 Atlantic, it may be safely predicted that the distribution of tempera- 

 ture will be represented by isothermal lines possessing the same general 

 character as those which have been laid down by me in this and 

 former Essays on the subject. 



1 See Appendix E to "Eeport on Oyster Culture," p. 68. 1870. 



