132 



Notes on the Meteorology 



valleys of the Tambo and other streams from the seaboard, 

 at a mean elevation of 3000 feet, and settling on the ranges 

 round Omeo, causing a rapid fall of the temperature. These 

 fogs are, according to the old residents, generally the fore- 

 runners of dry seasons, and are altogether distinct from the 

 ordinary radiation fogs of Sir M. Herschel.* Last Christmas, 

 while botanising on Mount Kosciusko, an opportunity was 

 afforded the writer of watching the progress of one of these 

 southern fogs coming from the seaboard. A warm cloudless 

 morning, with the thermometer 92 in the sun, at an eleva- 

 tion of 7000 feet at one p.m., was followed by a warm 

 cloudless afternoon ; until five p.m. large masses of what 

 appeared to be dense nimbus clouds were seen on the 

 southern horizon; these gradually enlarged, and could be 

 seen surging up the valleys. At last the temperature sank 

 to 43° Fahr., when a dense fog suddenly enveloped the summit 

 of the mountain, and in a few minutes began to clear off 

 again, sinking to a level of about 6000 feet, and there 

 remained like a wide- expanse of silvery ocean during the 

 clear moonlight night, until dissipated by the warm golden 

 rays of the rising sun. A peculiar feature of such fogs is 

 that the upper part is cooler than the lower— -i.e., when the 

 fog-masses are rising radiation of heat is greater at the upper 

 than at the lower part. 



Clouds. 



The following table shows the mean or average number of 

 days upon which the sky was overcast, cloudy, and clear at 

 nine a.m. for each month of the year. These results are 

 obtained from the daily observations between 1st April, 

 1879, and 1st November, 1884 :— 



Months. 



O'cast. 



Cloudy. 



Clear. 



Months. 



O'cast. 



Cloudy. 



Clear. 



January 

 February 

 March 

 April 

 May . . 



3 



2-8 



4-8 



5 



5 



3-4 



7 



14-6 



13 



16-6 



17-5 



17-3 



16-3 



13-7 



13-4 



12-2 



9-6 ! 



7-5 



8-9 



10-3 



10-3 



August 

 September . . 

 October.. 

 November 

 December 



5-3 



9 



4 



3-5 



3 



14-2 

 11-7 

 16-8 

 16-3 

 16-8 



11-5 

 10-1 

 10-2 



io-2 



9-2 



July . . 



Yearly Average 



55-8 



184-8 



123-4 



Scott's Meteorology, p. 121. 



