OF TEMPERATURE AT TORONTO IN CANADA. 
151 
be perseveringly maintained by a single observer. When there are two or more 
observers, there is no difficulty in multiplying the times of observation so as to com- 
prehend all the objects that may be desired, each in the manner and by the means 
which are most suitable to it and will be most satisfactory. But as the work of 
observation at by far the greater number of meteorological stations is usually carried 
out by a single observer, and as this is likely to be always the case, it should be a 
primary object with meteorologists who are furnished with sufficient means, to form 
tables of corrections to the mean daily temperature for every hour of the day, upon 
the basis of a sufficient number of years of observation, to be used at the respective 
localities, or within the distances to which such tables may be severally applicable, 
by persons whose means or convenience may restrict them in respect to the number 
and choice of hours of observation. With such a table, similar to Table III. of this 
paper, the choice is disembarrassed of its chief difficulty, that of selecting hours 
which by their combination will give an approximate mean temperature for the 
several months and for the year ; and the observer is left free to give a preference, 
independent of such consideration, either to the hours when the phenomena change 
least rapidly, and when consequently small irregularities in the times of observation 
will be least injurious, or to the hours which will furnish the best approximation 
to the daily maxima and minima of the meteorological elements generally, viz. of the 
temperature, the tension of vapour, the pressure of the gaseous atmosphere, and the 
force of the wind ; or to the hours which will have the most effective bearing upon 
other points of meteorological or climatic interest, to which the observer’s attention 
may be directed. 
The equation of the mean annual variation of the temperature, in the form most 
convenient for use, deduced from the twelve monthly means in the lowest horizontal 
line of Table I., is as follows ; — 
^,= +44°-32-21°-57sin (a+82° 58') + 0°-81 sin (2fl!-l-278° 32') 
- 1°'43 sin (3a-f333° 48')-l-0°-44 sin (4a+30° 04') 
-I- 0°73 sin (5a-l-37° 48') -f-0*32 cos 6a, 
in which a = nx30°, n denoting the number of months and parts of a month between 
January 15th and x. 
The equation of the mean diurnal variation of the temperature deduced from the 
twenty-four hourly means in the last vertical column of Table I. is — 
44°-32-b5°-513 sin (a-l-53° 40') + 0°-82 sin (2a-l-59° 08') 
-0°-48sin (3a-f41° 4l')-0°-06 sin (4aH-51° 23') 
-l-0°-04 sin (5a-|-20° 35'), 
in which a=nx 15°, n being the number of hours and parts of an hour between x, 
and 0 hours or astronomical mean noon. 
I now proceed to the second portion of the series, or to the six years in which the 
X 2 
