Notice of the Rarer Atmospherical Phenomena in 1824. 51 



by a line about 3° broad, through which the azure of the sky 

 could be seen throughout its whole extent. In a very few mi- 

 nutes after this was first observed, the cirrostratus partly dis- 

 solved, and partly inosculated with others; but the line of di- 

 vision still existed, and it now began to incline towards the 

 east ; in its course always observing perfect rectilinearity, and 

 dividing every cloud in two through which it passed, and 

 sometimes several at once. It made no progress towards the 

 zenith, but inclining more and irtore to the east, it became 

 at length almost horizontal, and gradually disappeared. 



It has been said, that the pressure was considerable during 

 the time of its occurrence ; but, in the course of two hours, it 

 began to diminish very rapidly, and in less than twenty hours, 

 the barometric column had fallen one inch. A gale of wind, 

 and much rain followed. The rain continued for three days. 



Nothing very particular occurred in April, except a 

 fine Solar Halo, which was seen on the 6th at sunset. 

 The sun's southern limb was within a few degrees of the 

 horizon. The sky was veiled by a general, but delicate 

 cirrostratus, and the sun was partially obscured by den- 

 ser clouds of the same kind. The halo was a simple one, 

 and of a uniform white colour throughout its whole extent. 

 The perpendicular radius was considerably greater than the 

 horizontal one, perhaps in the proportion of 42° to 35°. At the 

 same time, there appeared a perpendicular column of light ris- 

 ing from the position of the sun to the circumference of the 

 halo. (Therm. 47°, Bar. 30.40., wind N. E.) The day had 

 been remarkably fine. Immediately after sunset, and the 

 disappearance of the halo, a dense cirrostratus formed, which 

 continued all night and all next day. April was, on the whole, 

 a very pleasant month, the temperature rather above the mean, 

 and the pressure by no means variable. 



The weather during May was very agreeable ; rain fell on 

 five days. The mean temperature was about 50°, and the 

 sun's force sometimes very great. The maximum of tempera- 

 ture and the maximum of pressure both occurred on the 27th 

 day, at the time of new moon. The thermometer rose to about 

 80° in the shade that day. 



About half-past 6 P. M. of the 1st, while the sky was par- 



