The Rev. H. Lloyd on the Meteorology of Ireland. 425 



corresponding coast stations. Thus the mean temperature of Armagh (48'-6) 

 is less than that of Donaghadee by 1°, and less than that of Killough by I'^-G. 

 The mean temperature of Markree (48°- 2) is less than that of Killybegs by 

 2°-6, and than that of Westport by 3°'5. The mean temperatures of Portar- 

 lingtou and Athy (47"'3 and 48''4) are in like manner in defect, when compared 

 with those of Dublin and Courtown, and by an intermediate amount. I shall 

 return to this subject hereafter, and merely notice it at present for the purpose 

 of observing that no satisfactory conclusion can be drawn as to the dependence 

 of temperature upon geographical position, unless the inland and coast stations 

 be compared separately. 



Confining ourselves for the present to the coast stations, which are the 

 most numerous and the most widely distributed, we observe that there is an in- 

 crease of mean annual temperature in proceeding /rom north to south of the 

 island, the mean temperature of Portrush and Buncrana being 49°'0, and that 

 of Dunmore, which is nearly on the intermediate meridian, 51°'6. Similarly 

 there is an increase of temperature in proceeding from east to icest, the mean 

 temperature of Killough and Dublin being 50'-2, and that of Westport, which 

 is nearly on the intermediate parallel, 51°-7. 



But for an accurate determination of the rate of increase of temperature 

 in the two directions, it is necessary to combine the results by the method of 

 least squares. For this purpose let t denote the observed mean temperature 

 of any month, at any given station ; T the probable temperature of the same 

 month at an assumed central station ; and let the distances (in geographical 

 miles) of the former from the latter, measured on the meridian and perpen- 

 dicular to the meridian to the north and west, respectively, be denoted by y 

 and X ; then, if V and U be the increase of temperature corresponding to a 

 single mile in each direction, 



t= T+rx+ Vy. 



There will be a similar equation for each station ; and combining them by the 

 method of least squares, we shall obtain the most probable values of the un- 

 known quantities T, U, and V. 



The simplest mode of employing this method in the present instance is to 

 take, as the arbitrary central station, that whose latitude and longitude are the 



