THE CURRENTS OF THE ATLANTIC. 380 



inland stations were in defect, as compared with the coast stations. 

 The cause of this is obviously their greater distance from the 

 warm waters of the surrounding sea; and it follows evidently 

 from the fact, that the actual isothermal lines in Ireland are 

 inflected in passing from the sea to the land, and must even, in 

 part of the island as Mr. Hennessy has pointed out take the 

 form of closed curves, dependent on the position of the places 

 traversed with respect to the coast-line, as well as upon their 

 longitude and latitude. To determine such curves with exactness 

 would require a far greater number of stations than those em- 

 ployed, and would not seem likely to yield results of corresponding 

 value. The most feasible course seems to be to determine, in the 

 first instance, the law of distribution of temperature depending on 

 geographical position alone ; the disturbing influence of the land 

 can afterwards be computed approximately, and allowed for. 



Dealt with in this manner, the observations show that, on the 

 mean of the whole year, the isothermal lines are inclined to the 

 meridian by the angle N. 49 W., and that the temperature 

 increases, in a direction perpendicular to these lines, at the rate of 

 1 Fahr. for 89 miles. 



"We learn further, that the mean isothermal lines for the entire 

 year furnish a very inadequate representation of the progression of 

 temperature, and that, when the course of these lines is traced 

 from month to month, they vary within very wide limits. The 

 extreme positions correspond to the months of June and December. 

 In the former, the inclination of the isothermal lines to the 

 meridian is N. 106 W. ; in the latter, it is N. 9 W. Thus 

 these lines vary in direction 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. The rate of increase of 

 temperature changes little. 



The mean yearly temperature for the central station, whoso 

 latitude and longitude are the arithmetical means of those of the 

 stations of observation, is 50-3. It is thus distributed throughout 

 the year : 



