22 ~=Professor J. D. Everett’s Description of a Method 
It will be sufficient to calculate the values of a and e, and the 
mode of doing this is shown in the subjoined example, in 
which the proposed method of reduction is applied to the 
monthly mean temperatures of Stornoway for the average of 
the three years 1856-—7—8, as contained in the Report of the 
Scottish Meteorological Society, for the quarter ending June 
30th, 1859 :— 
37°5 | 54:4 S, | —16:9 | —16-9 | 8S 
38°8 | 57-0 S, | —25:9 | — 65 | S, | —3:25 
38°9 | 52:1 S, |— 94]— 76 | S, | —6°58 
43°2 | 46°8 S — 36 | S, | —3°6 
48:1 | 42:5 6 )—52°2 6)—13-43 
534 | 41:7 P= — 8:70 Q = —2:24 
tan. ¢ = a = tan. 75° 34’ Q.sec.¢c =—8'99 =a. 
The numbers at the head of the columns are simply for 
reference in the present description. 
Column 1 contains the temperatures of the six months 
January to June, and column 2 those from July to December. 
By subtracting the numbers in column 2 from those opposite 
to them in column 1, the numbers in column 3 are obtained, 
and the two last of these are written in reverse order in the 
second and third lines of column 4. 
By subtracting the numbers in column 4 from those oppo- 
site to them in column 3, as far down as the fourth line, we 
obtain the numbers in column 5. 
The symbols S,, S,, 8,, S,, in the next column, denote re- 
spectively the natural sines of 90°, 60°, 30°, and 0°, which are 
1, 866, 4, and 0. Multiplying the numbers in column 5 by 
these quantities, we obtain the numbers in column 7, which 
are then added and their sum divided by 6. The quotient is 
called P. 
Column 8 is obtained by adding the numbers in column 3 
to those opposite to them in column 4, The numbers in 
column 8 are then multiplied respectively by S,, S,, 8,, and 
S,, and the products form column 10, which must be summed 
and divided by 6. The quotient is called Q. 
