J. D. Everett on Reducing Observations of Temperature. 21 
dle of the first month. This leaves 64° 20’, which is the inter- 
val from the beginning of the cold half to the end (or begin- 
ning) of the year. The complement of this or 25° 40’ is the in- 
terval from the beginning of the year to the centre of the cold 
ae which again is 180° distant from the centre of the warm 
25° 40’ corresponds to 26 days (nearly) 
205° 40’ 6 “909 « “ 
The 26th and 209th days of the year are January 26th and July 
28th, which are therefore the centres of the cold and warm halves 
of the year, for the mean of the stations. The corresponding 
dates for any particular station, will be later or earlier than 
these by the amounts shown in the fourth column. : 
An expeditious method of finding the centre of the cold half is 
to assume the complement of E, as representing the interval 
from Jan, 15th to the required centre. hus the complement o 
70° 20’ is 10° 40’ corresponding to 11 days nearly, hence the cen- 
tre of the cold half is 11 days later than January 15th. This 
determination it will be observed coincides with that above 
given. In like manner the centre of the warm half will be 11 
days later than July 17th. 
y taking the sum and the difference of A, and A, we should 
obtain approximately the mean temperatures of the warmest and 
coldest groups of 30 days; or if the difference between the tem- 
peratures of these two periods is required, it can be foun 
simply doubling A,. These determinations are however only 
first approximations, and this is my reason for omitting them, 
all the numbers contained in the Table being second approxima- 
tions at least. 
With the joint purpose of testing the powers of the method, 
A, and K, for single years for a few of the Society’s stations, 
including three (the first three) which are not contained in the 
1857 to 1858, although the absolute times differ by nearly a 
fortnight. The amplitudes are also less for these two stations 
than for an others, the amplitude (and consequently the range) 
at Bressay Slings only about four-fifths of the average derived 
from the 24 stations, The extreme lateness of Thurston (near 
Dunbar) seems to be borne out by the results from single years, 
a8 appears from a comparison with the neighboring station, Kast 
n. The extreme earliness of Yester cannot be so satisfac- 
