APPENDIX NO. XI. 
407 
this instance easily explained. The two instruments were fac-similes 
of each other; any errors of division of the scale or from the unequal 
contraction of the fluid, which was the same in both and the same in 
quantity, and probably taken from the same preparation of spirits, 
were of course common to both. The error induced by the coloring 
matter of the fluid adhering in small particles to the sides of the 
tube became very marked at low temperatures. 
Our routine of daily observation was as follows:—Two 36-incli 
register spirit thermometers were noted hourly, as well as a varying 
number of instruments of smaller size. For purposes of comparison, 
the long spirit thermometers, and from five to twelve of the others in 
selected groups were generally read at the same time. The difference 
between the mean of these observations and the reading of any one 
instrument gave the correction which was applied to that instrument, 
in order to get the true or most probable temperature. 
I add here a table, containing the comparisons from which the 
corrections of the spirit thermometers actually in use between the 
temperatures of —68° and —20° are derived. The comparisons for 
temperatures between —20° and -f-36° are not given in the table, as they 
are very numerous; and the corrections of all our thermometers ran 
so regularly within these limits that their details would have little 
interest. 
In the following table S denotes the long 36-inch spirit thermo¬ 
meters, M the mercurial of the same construction. All the rest 
are alcoholic thermometers of from twelve to eighteen inches in length 
of scale. 
The appended table was compiled by Mr. Sontag directly from the 
original register. It is arranged according to the temperatures, com¬ 
mencing with the lowest. 
Table of Comjmrisons of Spirit Thermometers. 
1854 
February 5. 
February 5. 
February 4. 
Therm. 
Head. 
Corr. 
Therm. 
Read. 
Corr. 
Therm. 
Head. 
Corr. 
No. 12 
—80*0° 
H-12'0° 
No. 12 
—77*9° 
+13*0° 
No. 12 
—78*2° 
+14*0° 
1 
—75*5 
+ 7*6 
4 
_72*7 
+ 7*8 
4 
-7-1*0 
+ 9*8 
4 
—750 
+ 7*0 
2 
—69*0 
+ 4*1 
C 
—63*0 
— 1*2 
2 
—72*0 
4* 4*0 
8 
—67*5 
+ 2*6 
ss 
—57*8 
— 6*4 
8 
—70*5 
+ 2*5 
C 
—02*5 
— 2*4 
A 
—56*2 
— 8*0 
9 
— r,y*s 
+ D8 
s 
—58*3 
— 6*6 
B 
—5(3*0 
— 8*2 
9 
—67*0 
— 1-0 
A 
—56*0 
— 8*9 
Mean 
—64*2 
C 
—64-6 
— 3*4 
B 
—55*5 
— 9*4 
S 
—00-3 
— 7*7 
Mean 
— 64*9 
A 
—57-0 
—11*0 
13 
—50*4 
—11*6 
Mean 
—68*0 
