G34 
LIEUT.-GENERAL R. STRACHEY ON HARilOXIC ANALYSIS OE 
I am not in a position to indicate, further than has already been done, any direct 
or precise relation between the observed thermometric results thus recorded, and the 
varying place of the Sun, on which in combination with the latitude and local influ¬ 
ences of different descriptions they doubtless depend. The intermittent character of 
solar heat introduces a discontinuity of action which renders its connection with the 
j-esulting- phenomena sjjecially difficult of representation by algebraical expressions. 
Acting on a suggestion of Professor G. Darwin, I have calculated the harmonic 
constants that would, rejiroduce a curve indicating an intermittent action such as that 
of the Sun, continuing only during a portion of the day, and commencing and ending 
abruptly at sunrise and sunset. The results are of some interest, and serve to throw 
light on the character and signification of the harmonic components of temperature 
that have been under discussion. 
Such a calculation obviously disregards all cooling effects, and only deals with the 
Sun’s heating action, which 1 have assumed to be proportional to the sine of his 
altitude ; and with a view to obtaining figures in some degree comparable with those 
obtained from actual observation, and following the analogy of the value of P^, as 
previously pointed out, the total heating effect has been taken to be ten times the 
sine of the Sun’s altitude, the power of a vertical Sun being that represented by ten. 
On this assumption I have calculated the Sun’s altitude for each hour of the day 
for midwinter, the equinox, and midsummer for certain selected latitudes, and 
corresponding heating effects. These computations supply a series of hourly values 
having their maximum at noon and becoming zero at sunrise and sunset, and dis¬ 
appearing so long as the Sun is below the horizon. Treating these in the usual 
manner, the resulting harmonic components as far as the fourth order are shown in 
the following Table F ;— 
Table F. 
Midwinter. 
Ecpiinox. 
Midsummer. 
Latitude. 
Components. 
Components. 
Components. 
1\- 
l’;3- 
Pn 
Pi- 
Pj- 
P.. 
•) 
P.r 
Pi- 
It,. 
P 
S‘ 
P .r i 
O 
0 
-4-58 
^1-92 
0 
•40 
— o^OG 
-1-2-14 
0 
— ‘45 
-4-58 
+ 1-92 
0 
. 
-•40 ! 
20 
-3-40 
+ 1-70 
- -26 
— 
•30 
-4-74 
+ 2-02 
0 
-•43 
-5-25 
+ 1-74 
+ 
•29 
-•30 
.30 
-2-76 
+ 1-42 
- -28 
— 
•n 
-4-35 
+ 1-68 
0 
-•37 
— 5'27 
+1 -55 
+ 
•38 
-•21 
40 
-1'92 
+ 1-23 
- -43 
— 
•06 
-3-86 
+ 1-60 
0 
-•35 
-5-12 
+ 1-22 
+ 
•43 
-•05 
4.5 
-1-51 
-M-03 
- -42 
+ 
•03 
-3 52 
+ 1-49 
0 
-•35 
-5-19 
+ 1-05 
+ 
'37 
+ •06 
5J4 
-LOl 
+ -77 
- -39 
+ 
•12 
-3-15 
+ 1-.33 
0 
-•30 
-4-76 
+ -79 
+ 
•40 
+ '1S 
65 
0 
0 
0 
0 
-2-21 
+ -OS 
0 
-•20 
-3-85 
0 
+ 
•05 
+ •09 
As from the nature of the hypothesis adopted the diurnal curve analysed is in all 
cases symmetrical on either side of noon, the values of (j are all zero. Also the values 
