le ee ee 
} 
401 
The President also exhibited to the Academy a diagram, 
representing the diurnal changes of temperature during the 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 Pp. 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 . . | 6th. | 7th. | 8th. | 9th. | 10th.) 11th.| 12th.| 13th.) 14th. 
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- 
eurred 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°. 
