434 The Rev. H. Lloyd on (he Meteorology 0/ Ireland. 



numbers accordingly exhibit the law of the annual variation of sea temper- 

 ature, around the coasts of Ireland ; and the remarkable regularity in their 

 progression shows that, even from the results of a single year, we obtain a 

 close approximation to the actual law. 



We learn from these numbers that the annual change of the sea temper- 

 ature, at the surface, differs considerably from that of the air above it, the 

 difference consisting chiefly in a retardation of the epochs of maximum and 

 minimum. Thus the minimum temperature occurs in the middle of February, 

 and the maximum in the middle of August, — or about a month after the cor- 

 responding epochs of the temperature of the air. The annual range is also, as 

 might have been expected, considerably less than that of the air. These re- 

 sults accord sufficiently well with the conclusions drawn by KiEMTZ, from a 

 comparison of the results of many voyagers. 



But the most interesting result is that concerning the relation between the 

 temperature of the sea at the surface, and that of the superincumbent air. Upon 

 this subject the greatest discordance exists in the statements of different ob- 

 servers. According to Humboldt, the mean temperature of the Atlantic 

 Ocean, at the surface, is in all cases higher than that of the atmosphere above it- 

 This conclusion is confirmed by the observations of Peron and Fitzeoy, and is 

 contradicted by those of Irving, Forster, and Kotzebue. From an elaborate 

 discussion of the observations of many voyagers, K^mtz infers that the temper- 

 ature of the sea is less than that of the air over the land in the lower latitudes, 

 while in the higher latitudes it is <j r eater ; the difference seldom, however, ex- 

 ceeding 1° Fahr. The original conclusion of Humboldt, however, seems to be 

 placed beyond all doubt by the recent observations of Captain Duperrey, which 

 appear to be more numerous, and taken with more precautions to insure accu- 

 racy, than any preceding. It seems now to be generally admitted that, in the 

 temperate and folar regions, the temperature of the sea is A/^Aerthan that of the 

 air ; and the only question that remained was as to the tropics. Now the ob- 

 servations of Duperrey were made all round the globe, between 10° N. and 

 10° S. latitude ; and they were taken at intervals of four hours, so as completely 

 to eliminate the effects of the diurnal change. From these observations it ap- 

 pears that the temperature of the sea is higher than that of the air within the 



