ON THE METEOROLOGY OF IRELAND. 



335 



We learn that the defect of temperature due to inland position 

 is, as might have been expected, least in summer and greatest in 

 winter. A small part of this defect is due to elevation ; but it is 

 easily eliminated. The mean height of the instruments at the coast 

 stations above the level of the sea is 30 feet. We have, therefore, 

 only to subduct' this from the known heights at the inland stations, 

 and to correct for the difference of level at the rate of 1 Fahr. for 

 276 feet, which is the mean of the determinations made by Mr. 

 Welsh in his balloon ascents, for the lower portion of the atmo- 

 sphere lying beneath the great vapour plane. The mean yearly 

 results at the four inland stations, thus corrected, are as follows : 



DIURNAL EANGES OF TEMPERATURE. 



Climatology depends upon the ranges of temperature (whether 

 diurnal, monthly, or annual), no less than upon mean values; and 

 their investigation is accordingly a necessary part of the present 

 inquiry. In the present series of observations, the diurnal ranges of 

 temperature are given by means of the results obtained with self- 

 registering thermometers. These results are the least satisfactory 

 portion of the whole series. It is well known that the ordinary 

 self -registering thermometers are extremely apt to get out of order, 

 the maximum, by the index becoming entangled in the mercury, 

 and the minimum, by the distillation of the spirit into the upper 

 part of the tube ; and although the observers were carefully in- 

 structed in the mode of remedying these derangements, no one (I 

 believe) who has handled such instruments will wonder that men 

 previously unaccustomed to them should have sometimes failed, in 

 what is in all cases a somewhat delicate operation. 



