162 
ON THE PERIODIC AND NON-PERIODIC VARIATIONS 
February and March appear to be months most liable to extreme variations ; July 
and August the least so ; the probable variability of the several months is as follows 
January ±27 April ±1-9 July. . ±1-1 October . ±]-4 
February ±2*6 May. +V8 August. ±1*2 November. ±2-1 
March . ±2-8 June. ±2-0 September ±1-8 December. ±2-5 
The mean annual temperature derived from the whole body of the observations in 
twelve years is 44°'23 ; and on the supposition that no constant errors, instrumental 
or observational, or occasioned by insufficient protection or defective exposure of the 
thermometer, are involved, and that the variations of the temperature in different 
years may be regarded strictly as accidental oscillations around a mean value, and of 
equally probable occurrence in every year, the probable error of this result is i0°-18. 
The probable variability of a single year is 4:0°*63 ; showing that there is an equal 
probability that the mean temperature of any one year will fall within the limits of 
43°-60 and 44°*86, as that it will exceed those limits ; a conclusion which perhaps 
would scarcely have been anticipated considering the great range of the thermometer 
in the course of the year, and the magnitude of the non-periodic variations in short 
intervals. The climate of Toronto presents a remarkable combination of great 
regularity in the annual temperature with great variability occurring in the course 
of the year. The mean temperatures of the several years differed from the average 
mean temperature as follows ; — 
1850. -fO-22 
1851. —0-25 
1852. —0-39 
184/. -0-53 
1848. +0'85 
1849. — 0-14 
1844. +0-25 
1845. +0-35 
1846. +2-13 
1841. —0*31 
1842. -0*27 
1843. — 1-88 
The excess of cold in 1843 (1°*88) was due chiefly to the occurrence of very low 
temperatures in February and March of that year ; the excess of heat in 1846 (2°-13) 
was more generally diffused throughout the year, all the months excepting February 
and October being above their average. 
Table VI. exhibits also the normal temperatures of the different months m the 
geographical latitude, 43° 40' N., in which Toronto is situated, taken from Dove’s 
^ Verbreitung der Warme,’ Berlin, 1852 ; as well as the ‘ Thermic Anomaly,’ or differ- 
ences between these normal values and the temperatures observed at Toronto. It 
appears from this comparison that every month of the year at Toronto is colder than 
the normal temperature of the parallel in which it is situated, the mean annual 
temperature being nearly 7° below the normal. The thermic anomaly is least in 
July and August (between 2° and 3°) and greatest in February, when it exceeds 1 1°. 
Its sudden increase in October and decrease in November are deserving of notice. 
In viewing the bearing of the thermic anomaly at Toronto on the more general 
question of the thermic anomaly in the part of North America in which it is situated, 
