401 



The President also exhibited to the Academy a diagram, 

 representing the diurnal changes of temperature duringthe late 

 remarkable depression, which occurred in the week commenc- 

 ing February 7. The observations from which it is taken 

 are those made at the Magnetical Observatory of Trinity Col- 

 lege, at six stated hours during the day, together with those 

 of the maximum and minimum temperature, furnished by self- 

 registering thermometers. The following Table exhibits the 

 mean temperature for each day ; the maximum and minimum 

 of temperature ; and the difference of the latter, or the diurnal 

 range. The mean temperature is deduced from the observa- 

 tions at 10 A.M. and 10 p. M., except on the two Sundays, 

 when it is inferred from the maximum and minimum tempera- 

 tures. The Table includes the day preceding and that follow- 

 ing the depression : 



Day of Month . . 



Mean Temp. . . 

 Maximum .... 

 Minimum .... 

 Range 



6th. 



7th. 



8th. 



9th. 



10th. 



nth. 



12th. 



13th. 



14th. 



43.0 

 50.5 

 40.0 

 10.5 



33.8 



34.5 



33.0 



1.5 



29.6 



34.8 



26.0 



8.8 



28.4 



33.2 



25.2 



8.0 



30.8 



35.5 



25.7 



9.8 



31.9 



34.6 



24.7 



9.9 



24.2 

 30.3 

 21.5 



8.8 



35.6 

 47.5 

 16.7 

 30.8 



45.5 

 51.2 

 39.8 

 11.4 



The greatest depression took place on the morning of the 

 13th, the minimum temperature being 16°, 7.* A registering 

 thermometer, exposed to radiation towards the sky, exhibited 

 at the same time the temperature 12°.0. Temperatures so low 

 as these, although not uncommon in England, have not oc- 

 curred for many years in this country. The range of tempe- 

 rature, otherwise pretty constant, was remarkably affected on 

 the first and last days of the depression (the 7th and 13th), 

 the decrease of temperature on the former day reducing it to 

 1°.5, while the increase on the latter raised its amount to 30°. 8. 

 In fact, on this day (the 13th), the rise of temperature was so 

 rapid, and so continuous, that the day maximum was entirely 



* At Mr. Yeates' house, on the south side of Dublin, the minimum ther- 

 mometer registered 11°. 



