MADE BY CAPTAIN BACK DURING HIS LATE ARCTIC EXPEDITION. 
403 
Therm. L. 
Differences. 
Therm. N. 
Values of 
m 
"M* 
Differences. 
Difference in 
value of — 
M 
corresponding 
to difference of 
1° in Therm. L. 
47-0 
78-4 
46-8 
O 
31*4 
31-6 
65*2 
67*0 
65-5 
•2900090 
•2863406 
•2887895 
•0036684 
•0024489 
•0001168 
•0000775 
Mean. . . . 
•0000972 
7YI 
Taking - the mean of the values of corresponding - to the indications 47° - 0 and 
Til 
46°’8 of the thermometer L, we have - 2893993 as the value of corresponding to 
the temperature 46 0- 9 of the needle L. Subtracting from this '0000972 x 13*1, or 
*0012733, we have '288126 for the value of ^ at the temperature 60°. If we take 
the value of ^ at the temperature 60° to be 1, we shall have. 
The increment in the value of ^ for each 1° above or below 60° = *0003374. 
Substituting the times in the second set of observations in the equation (16.), we 
obtain the following results : 
Therm. L. 
Differences. 
Therm. N. 
Values of 
m 
U* 
Differences. 
Difference in 
value of ~ 
corresponding 
to difference of 
1° in Therm. L. 
47-6 
78-5 
49-6 
O 
30-9 
28-9 
59°-8 
60-3 
60-1 
•5360947 
•5i 91772 
•5341648 
•0069175 
•0049876 
•0002239 
•0001726 
Mean. . „ . 
•0001982 
711 
From these, taking a mean as before, we obtain *5351298 as the value of ^ cor- 
responding to the temperature 48°*6 of the needle L; and subtracting *0001982 X 1 1*4 
711 
from this value, we have *5328704 for the value of ^ at the temperature 60°. Taking 
771 
the value of at the temperature 60° to be 1, we have, 
771 
The increment in the value of ^ for each 1° above or below 60° = -j- *0003719. 
The mean of the two results gives 
771 
The increment in the value of for each 1° above or below 60° = if *0003546. 
We therefore obtain, for the correction of observations made with the Lozenge- 
needle, the equation 
* = 1 + -0003.5461 * ‘ * ( 1 "* L-) 
3 F 2 
