4 Proceedings. 



" The halo I am referring to is the ring of light, generally 

 slightly coloured, which is occasionally seen surrounding 

 the sun at an angle of about 22°. The explanation of the 

 halo is to be found in the refraction of light through small ice 

 crystals. The halo is generally seen in front of a cyclone, 

 and is considered a prognostic of bad weather. The 

 following observations will show, however, that the 

 prognostic is by no means as certain as it is sometimes 

 supposed to be. On Tuesday, the 25 th September, about 

 12 o'clock, the sky above the Zermatt Valley became 

 pretty suddenly covered with a thin film of cirrus clouds, 

 and a halo appeared surrounding the sun. The barometer 

 during that day was rising slightly. The sky cleared in 

 the afternoon, and the two succeeding days were perfectly 

 fine. On one of these days — I am sorry to say I have not 

 kept a record which it was — another halo was seen by 

 others, though not by myself. On Friday, the 28th, the 

 sky clouded over during the morning, and there was a 

 drizzling rain in the afternoon, the barometer keeping high 

 all the time. It cleared about 4 a.m. on Satur lay and 

 remained perfectly clear that day. I have not, unfortunately, 

 access to the Swiss weather charts, but I understand that 

 there was much bad weather on the Italian side of the Alps 

 during the days the halos were seen. Cirrus clouds, 

 supposed to be ice-clouds, are often seen without the halo, 

 and there is, a priori, no reason why halos should only be 

 seen in that kind of cirrus sky which lies in the front of 

 the track of a cyclone, but observation seems to point in 

 that direction. Halo prognostics are known to break down 

 when a cyclone changes its direction, but it is also possible 

 that in the high regions of the Alps the atmospheric 

 conditions are somewhat different than over plains. At 

 any rate, a more systematic record of all visible halos seems 

 called for, especially in the districts which contain mountains 

 of high altitudes." 



