ON THE HOURLY OBSERVATIONS OF THE THERMOMETER. 195 
1833 and 1834. 
Mean maximum . 
Mean minimum ... 
Mean temperature of 10 days about the summer solstice 
Mean temperature of 10 days about the winter solstice 
Mean temperature of the four 
seasons, from 4380 observa- 
ing 3 months each 
Mean temperature of winter 
and summer, from 8760 ob¬ 
servations, by Table VIII., 
including 6 months each ... 
Winter, viz. Jan., Feb., Dec. .. 
Spring, viz. March, April, May 
tions, by Table VII., includ- ] Summer, viz. June, July, August 
Autumn, viz. Sept., Oct., Nov. 
Winter, viz. Jan., Feb., March, 
Oct., Nov., Dec. 
. 80* 
.30* 
,58*185 
,46*540 
,46*57 
50*55 
, 60*50 
, 53*93 
47*955 
Summer, viz. April, May, June, \ 57 - 39(5 
b \ 
July, Aug., Sept.,/•** 
Mean temperature of the two years, from 17,520 observations, by \ 
Table VII./ 
Mean temperature of October, the nearest to the mean of the two years .. 
Extreme range from the mean of the two years. 
Mean range from the mean of the two yeais... 
52*90 
54*60 
50* 
9*871 
Daily Progression of Temperature . 
The daily temperature for each hour for each of the years 
1833 and 1834, together with the mean of the two years, is 
projected under the form of curves in Plate VI., from the num¬ 
bers in the last columns of Tables II., IV., and VI. The dot¬ 
ted curved lines represent the progress of the daily temperature 
at Leith. 
Each point of the mean curve is the result of 730 observa¬ 
tions, and each point of the curves for the separate years the 
result of 365 observations. From these it appears that the 
temperature is lowest at 5 a.m., after which it steadily increases 
until 1 p.m., when it again descends to the minimum. The pe¬ 
riod of ascent being eight hours, and that of the descent sixteen 
hours, which numbers are in the ratio of 1 : 2. Taking the ra¬ 
pidity with which the temperature increases or decreases be¬ 
tween the points of maximum and minimum, through a given 
number of degrees, as inversely proportional to the times, we 
may conclude, in neglecting the intermediate changes, that upon 
the whole the heat of the day advances in this case with twice 
the rapidity of the cold of the night. The general agreement 
between the curves of the two years and the mean is very strik¬ 
ing, and shows a close approximation in the observations to the 
true form of the daily curve. On comparing these results with 
the hourly register at Leith Fort for the years 1824 and 1825, 
we observe, as shown by the dotted curved lines in Plate I., 
that the maximum does not take place at Leith until two hours 
after it occurs at Plymouth, whilst the minimum occurs at 
•» _ 
nearly the same hour. The curves also are, as might be antici- 
o 2 
