METEOROLOGY. 211 
The days of excessive abnormal. variation, in. which the mean pressure of the 
day differed by -200 inches, and upwards, from the normal, were 115, a number 
somewhat larger thar usual. The:law of their distribution among the months is 
not so well marked as in the case of temperature, but their greater frequency in 
the winter than in the summer months is sufficiently obvious, being 19 and 5 in 
December and August of 1860, and on the aggregate of four years, 50 in Decem- 
ber and 17 in August. If further the aggregate amounts of the abnormal vari- 
ations of all the observations in each month be compared, a law will be found to 
prevail in the distribution resembling very closely in its general character that 
just stated. 
Humidity —The mean humidity of the year was 77, which is rather in excess 
of that of the preceding year. Its distribution among the several months was 
more than usually equable. : 
Clouds.—The extent of sky clouded, in accordance with the experience of 
former years, amounted to $ of the hemisphere on the average of the year. July 
and August were the clearest months, and December the most cloudy. 
Wind.—The resultant direction of the wind was N. 60 W., (almost identical 
with that of 1859) and the resultant velocity 3-32 miles. The mean velocity was 
8°55 miles, which shows a still further increase on the velocity of the preceding 
year. The day of greatest wind was March 21, when the velocity averaged 28-83 
miles; and the calmest day was February 4, when the mean velocity was only 
0°85 miles per hour. The greatest velocity recorded for a whole hour was 40°6 
miles, from 8 p.m. to 9 p.m. on February 9. 
The most windy hours on the average of the year were from 1 P.M. to 2 P.M. 
and from 2 P.M. to 8 P.m., with a mean velocity in each case of 11:17 miles; and 
the calmest hour from 1 a.m. to 2 a.m., when the mean velocity was 6°91 miles, 
Rain and Snow.—The depth of rain was 23°434 inches, or nearly 10 inches less 
than in 1859, a deficiency having occurred in every month but February, July and 
August. The amount of snow (45:6 inches) was also below the average to the 
extent of 15:3 inches, and the rain and melted snow combined fell short of the 
average by 8589 inches. While the quantity of rain and snow was deficient the 
number of days on which rain fell was about 8 per cent., the number of days of 
snow 2 per cent., and the number of rain or snow about 5 per cent., greater than 
the average of the six years given in the annexed table. 
July was the most rainy month in respect to the amount of rain, and May in 
respect to its frequency. Even when snow is taken into account and reckoned as 
rain, July still maintains its predominance in the amouut of precipitation, but the 
maximum of frequency is then transferred to December. 
The heaviest fall of rain was 1°265 inches on December 19, and the heaviest 
fall of srow 9 inches on February 18. 
Thunderstorms.—Of the 81 thunderstorms recorded the earliest took place on 
February 22, and the latest on October 15. The storm of August 24 was one of 
great violence. 
Auroras.—Of the 58 auroras given in the table the most brilliant occurred on 
March 26, 27, and September 6 and 15. 
The following is the General Meteorological Abstract for the year 1860, deduced 
from the observations taken at the Provincial Observatory :— 
