338 0& THE METEOROLOGY OF IRELAND. 



TEMPERATURE OF THE SEA. 



Provision was made that the temperature of the sea should 

 be observed at all the places at which tidal observations were 

 taken. For this purpose each station was furnished with a 

 thermometer, having its bulb inclosed within a small reservoir of 

 copper, for the double purpose of guarding it from accident, and 

 of protecting it (by means of the contained water) from rapid 

 changes of temperature, when it was lifted into the 'air for obser- 

 vation. The observer was instructed to note its indications twice 

 in the day, at intervals of about twelve hours, the thermometer 

 being attached to a pole, and plunged to the depth of about one 

 foot in deep water. The diurnal change of the temperature of 

 the sea being very small, it is completely eliminated by two such 

 observations. At many of the stations the instrument was lost, or 

 broken, in the attempt to use it during boisterous weather. We 

 are, therefore, only in possession of the results from six stations, 

 which are contained in the following Table. 



In the last two lines of the Table are given the mean results 

 of the six stations, and the differences between them and the mean 

 of the entire year. These numbers accordingly exhibit the law 

 of the annual variation of sea temperature, around the coasts of 

 Ireland ; and the remarkable regularity in their progression shows 

 that, even from the results of a single year, we obtain a close 

 approximation to the actual law. 



