458 Experiments to determine variations in length of bars. 
For the comparisons of the glass meters G, and G,, the steel 
meter S, was used also as a standard, and the same program 
was followed as with the other bars. By accident, however, 
G, was broken just subsequent to the second set of comparisons 
after heating it. The results of these comparisons are given in 
the following tables. 
Differences in Length of Steel and Glass Meters. 
Date, 1883. G,—S, Mean. Remarks. 
February 20 +154°1 ia 
21 +1549} +154°9 Before heating G, 
+3 21 55°8 
“i 21 . +1591 : After heating 
“99 +1580 t dioeiste: G, to near 212° F. 
Differences in Length of Steel and Glass Meters. 
Date, 1883. 8,—G, Mean. Remarks. 
March 15 +40°8 Ku 
a3 4 > e 
“ : od +410 Before heating G, 
. 17 +384 
s 17 38°2 : 
After heating 
e 18 +37°8 38-2 3 
ts 19 439.3 Si G, to near 212° F. 
ss 20 39°4 : 
i 21 4+36°8 438-1 After a 7 
. 23 + 38°1 ar -6° F. 
The means of the groups of results before and after heating 
the glass meters indicate that each bar was slightly lengthene 
(at the temperature of melting ice) by the heating, the quantity 
has been heated to 212 
cubical expansion of mercury is about per degree 
F., a change of 0° F. in the position of the freezing: 
point of a thermometer would correspond to a linear change 
of gs}op or to 167 in the length of a meter. If, as <ndicatede | 
