436 The Rev. H. Lloyd on the Meteorology of Ireland. 



It follows also, that the absolute excess of sea temperature considerably ex- 

 ceeds that above stated. Thus, we have seen, the temperature of the sea, on 

 the average of the entire year, exceeds that of the air over the coasts by 2'''0 ; 

 while the latter temperature exceeds that of the air inland (for the same la- 

 titude and longitude) by l"-8. The total excess of the sea temperature above 

 that of the air amounts, therefore, to 3^'8 Fahrenheit. 



This excess, which appears to be much greater than has been observed 

 elsewhere, is to be ascribed, mainly, to the influence of the gulf-stream upon 

 the temperature of that part of the ocean which bathes our shores. But there 

 is likewise another cause which undoubtedly contributes also to the effect. It 

 has been shown by Mayer and Joule, that heat is generated by the friction of 

 fluids in motion, and the latter experimentalist has established the important 

 physical law, that there is a definite relation between the heat so produced, and 

 the mechanical power expended by the moving mass. Mr. Eankine has already 

 applied this principle to explain the fact, observed by M. Eenou, namely, that 

 the temperature of the river Loire at Vendome is higher than that of the air 

 above it ; and it is obvious that a similar explanation is applicable to the phe- 

 nomenon under consideration. There is no doubt as to the reality of the 

 cause ; the only question can be as to the magnitude of the efiect to be ascribed 

 to it. That such efi"ect is, at all events, sensible, I infer from two circumstances. 

 The first of these is, that the phenomenon of the excess of sea temperature appears 

 to be general, and must, therefore, be the effect of some general cause ; the se- 

 cond is, that on the coasts of Ireland there is no sensible difference between the 

 amount of the excess on the eastern and on the western shores.* 



Should the effect of this cause be found to be sensible, and its amount be 

 determined, our views of the cycle of meteorological phenomena would be much 

 enlarged. The elevation of temperature rarefies the air ; the denser air flows 

 in to supply the partial vacuum, and wind is produced ; and finally, this wind, 



* There is another corroborating circumstance which perhaps deserves also to be mentioned. 

 Most bathers have, I believe, noticed the fact that the sea appears warmer, cateris paribus, when 

 agitated than when at rest. I am not aware that any direct thermometrical measures have ever been 

 made to establish the fact thus evidenced by the senses ; and I need not say that, if established, it 

 would bear the whole weight of the hypothesis above proposed. 



