336 



OF THE METEOROLOGY OF IRELAND. 



But there is another source of error affecting the maximum 

 thermometer, which it is still more difficult to avoid. If the in- 

 strument be exposed to the influence of radiation for any portion 

 of the day, however short, it will, from its construction, retain the 

 impression made upon it ; and, consequently, if the abnormal tem- 

 perature to which it has been thus subjected exceeds the greatest 

 temperature of the air in the day, an erroneous result will be re- 

 corded. The difficulty of guarding thermometers completely from 

 such influences is well known; and although some trouble was 

 taken to insure this protection, the observations themselves show 

 that it was not effective at all the stations. I have, accordingly, 

 been compelled to reject a portion of the results obtained with the 

 maximum thermometer, as defective from this cause. 



In the following Table are given the diurnal ranges deduced 

 from the maximum and minimum temperatures, combined in 

 yearly and half-yearly periods, retaining only those stations at 

 which one or other of the two half-years is complete : 



DIURNAL BANGES (HALF-YEARLY AND YEARLY MEANS). 



