The Rev. H. Lloyd on the Meteorology of Ireland. 427 



The vahies of t/ and Fbeing known, the positions of the isothermal lines are 

 determined. The inclination of the isothermal lines to the meridian, measured 

 from north to west, m, and the rate of increase of temperature in the direction 

 perpendicular to them, TF, are known by the formula; 



Their values for the several months are given in the foregoing Table. 



We see then that, on the mean of the whole year, the isothermal lines are 

 inchned to the meridian by the angle N. 49" W.; and that the temperature in- 

 creases in a direction perpendicidar to these lines, by -0112 of a degree for each 

 geographical mile, or at the rate of 1 degree for 89 miles. The increase of 

 temperature, in proceeding from north to south, is V= -0085, or 1° in 118 

 geographical miles ; the corresponding increase, in proceeding from east to west, 

 is U— "0073, or 1° in 137 geographical miles. 



We learn further, that the mean annual isothermal lines furnish a very in- 

 adequate representation of the progression of temperature ; and that when we 

 follow the course of these lines from month to month, we find them to vary within 

 very wide limits. The extreme positions of these lines, as given in the preceding 

 Table, are those for the months of June and November. But the result obtained 

 for the latter month must, I think, be regarded as anomalous, on account of the 

 irregularity in the distribution of temperature already noticed ; and, rejecting 

 it, the extreme positions correspond to the two solstitial months. They are 



the following : — 



June, ... ?<=N. 106° W., IF = -0114, 



December, m = N. 9° W., W= "0104 ; 



so that the direction of the isothermal lines varies through an angle of 97° in the 



course of the year, being nearly parallel to the meridian in December, and nearly 



perpendicular to it in June. (See Plate vii.) 



We may now employ the formula 



t=T+ Ux+ Vy, 

 to deduce the probable temperature at any place, and compare it with that ac- 

 tually ofcer nee?; we shall thus find tlie effect due to local causes. Making this 

 calculation for the four inland stations, we obtain the results given in the fol- 

 lowing Table : — 



VOL. xxn. 3 K 



