190 Trmisactions of the Boyal Society of South Africa. 
construct a satisfactory teraperature curve based upon the most common 
differences of temperature between one hour and the next. There are 
some weak central values which, to some extent, disappear in the process 
of smoothing by Bloxam's method. If I am not mistaken these arise 
largely from a tendency to a concentration of the frequencies round differ- 
ences of whole degrees. Every reader of a meteorological thermometer 
probably has more entries in his register in whole degrees than in any 
fraction thereof : e.g., 50°*0 will occur more often than, say, 50°*2 ; and 
48°-0 more often than, say, 47°"9. Consequently the difference 2°-0 will 
occur more often than, say, l°-3. This is to be expected in a way, because 
the etched division indicating the degree, however fine it may be, has some 
breadth, and so takes up more of the scale than the imaginary divisions 
July Temperature Variation. 
Hour Ending 
Normal Curve. 
Component Curves. 
A. 
B. 
c. 
t-V. 
t-t'. 
t-t'. 
t—t'. 
I 
+ 1-2 
o 
+ 0-1 
o 
+1-1 
+ 2-0 
II 
+ 10 
+ 0-1 
+1-1 
+ 2-1 
Ill 
+ 0-7 
-0-1 
+0-9 
+ 1-9 
IV 
+ 1-0 
+ 0-2 
+ 1-2 
-1-9 
V 
+ 0-7 
0-0 
+ 0-9 
+ 1-9 
VI 
+ 0-5 
+ 0-1 
+ 1-0 
(+1-6) 
VII 
+ 0-7 
0-0 
+ 0-9 
+ 2-0 
VIII 
-4-3 
-3-0 
-4-0 
-50 
IX 
-8-0 
(-6-9) 
-7-9 
-8-9 
X. 
-5-5 
-5-0 
-6-1 
-6-9 
XI 
+ 4-2 
-3-1 
-4-0 
-4-9 
-3-0 
-2-3 
-3-1 
-3-8 
XIII 
-2-0 
-1-3 
-2-0 
-2-7 
XIV 
-1-2 
0-0 
-1-1 
-1-8 
XV 
-0-3 
+ 0-3 
-0-3 
-0-9 
XVI 
+ 10 
( + 1-6) 
+ 0-9 
0-0 
XVII 
+ 5-3 
+ 3-0 
+ 5-0 
+ 5-8 
XVIII 
+ 6-1 
+ 4-5 
+ 5-9 
+ 7-0 
XIX 
+ 2-8 
+ 1-9 
+ 3-0 
+ 3-5 
XX 
+ 2-0 
+ 1-0 
+ 2-0 
+ 2-9 
XXI 
+ 1-7 
0-0 
+ 1-9 
+ 2-9 
XXII 
+ 1-4 
+ 0-1 
+ 1-1 
+ 1-9 
XXIII 
+ 1-2 
+ 0-1 
+ 0-9 
+ 2-0 
Midnight 
+ 1-2 
+ 0-1 
+ 1-0 
+ 1-9 
