252 Prof. Heunessy on the Distribution 



bordering on the coast. For this purpose we should manifestly 

 compare a group of inland with a group of coast stations nearly 

 on the same parallel of latitude. The following are thus selected 

 from the Table of mean annual temperature of Ireland : — 



Inland Stations. 



The mean latitude of the coast stations is 6' greater than that of 

 the inland stations, and is thus slightly unfavourable to an excess 

 of temperature ; yet the mean temperature of the former exceeds 

 that of the latter by 2°*3. The mean difference in height is 139 

 feet ; consequently, if the greater warmth of the coast were due 

 to difference of elevation alone, the rate of decrease of atmo- 

 spheric temperature in ascending over ground lying at an almost 

 insensible mean inclination to the horizon, would be 1° for 60 

 feet. A supposition which leads to a result so discordant with 

 the best observations must be abandoned as altogether unte- 

 nable. 



Hitherto, distance from the sea has but rarely entered into 

 temperature tables, and then only for a limited number of 

 stations. It now appears to possess claims to be definitively con- 

 sidered as a fourth coordinate, and in the case of most of the 

 stations in the British islands it is undoubtedly the most im- 

 portant after latitude. In the accompanying Tables a column has 

 been accordingly appended, in which the value of this element 

 is given in English miles. The distances are all taken from 

 the maps published by the Society for the Diffusion of Useful 

 Knowledge. When a distance is taken from the mouth of a 

 river or estuary, it is generally not counted from the nearest 

 point of the coast, but from some point about midway between 

 the opposite shores of the inlet. 



The mean temperatures, marked D, are taken from Dove's 

 Table; those marked n, I have calculated entirely from other 

 sources; those unmarked are combinations of such results together 



