250 Prof. Hemiessy o« the Distribution 



conditions. Tlie western coast alone is backed by any consider- 

 able masses of elevated land ; and the interior is generally far 

 from being so flat as the inland portions of Ireland. Its position 

 with regard to the warmer and more prevailing winds, as well as 

 the magnitude of the Bristol Channel, indicates that this great 

 arm of the sea may exercise a remarkable influence on districts 

 in the valley of the Severn which might otherwise possess a cli- 

 mate similar to places more strictly inland. Lastly, the much 

 greater length of the island in the direction of the meridians, 

 compared to its mean breadth in the direction of the parallels, 

 would seem to point to a very different distribution of tempera- 

 ture from that which exists in Ireland. 



The observations on the temperature of the sea recorded in 

 Dr. Lloyd's memoir show that, in the Irish Sea and St. George's 

 Channel, as well as in the Atlantic Ocean, the mean tempera- 

 ture of the surface-water exceeds that of the air. A similar 

 result has been found by observations made on the surface of the 

 German Ocean at Scarborough, although the excess of the water 

 temperatui'e above that of the atmosphere in this case is not so 

 remarkable as in the former. It is to be hoped that Captain 

 Woodall, who announced this interesting fact at the meeting of 

 the British Association held in 1856 at Cheltenham, will publish 

 the observations which have led him to a result so important. 



As it thus appears to be placed beyond the possibility of 

 reasonable doubt, that the shores of Great Britain, like those of 

 Ireland, are washed by heat-bearing currents, I was prepared, 

 notwithstanding the diversity of configuration of the two islands, 

 to find some approach towards the re-entrant shape in the iso- 

 thermals of the former. In order to construct these lines, I 

 made use of the valuable Tables calculated by Professor Dove, 

 and printed in the Report of the British Association for 1847, 

 and of the quarterly returns of the state of the weather in 

 England, published by Mr. Glaisher. I have also availed 

 myself of some detached results which are not contained in 

 either of these collections. In Mr. Glaisher's returns will be 

 found the names of the observers to whose patience and devotion 

 to science we owe many of these interesting facts. 



Having calculated the mean annual temperatures for more 

 than fifty places not already in Dove's Table, and corrected a 

 few of his results by the aid of subsequent observations, I com- 

 bined them in approximately isothermal groups, precisely as I 

 had already done in the case of Ireland. The isothermal lines 

 laid down in the Map which accompanies this essay, have been 

 drawn by the aid of such indications, most weight being attached 

 to the results of the best observations. These lines are not in- 

 tended to represent with perfect accuracy the mean annual dis- 



