264 THE ATLANTIC. [ CHAP. IV. 
S Zin 
SS, 
Fria. 70.—Thermometer tubes broken 
by pressure at Station XXV. A, 
Thermometer No. 39; B, No. 42. 
bulb and the top of the tube. The 
large bulb and its covering shell were 
also broken, but into larger pieces, dis- 
posed as if the injury had been pro- 
duced by some force acting from 
within. The thermometer tube was 
broken through in three places; at 
one of these, close to the bend, it was 
shattered into very small fragments. 
The creosote, the mercury, and bub- 
bles of air were irregularly scattered 
through the tube, and it is singular 
that each of the steel indices had one 
of the disks broken off. The whole 
took place, no doubt, instantaneously 
by the explosion of the small bulb, 
which at the same time burst the 
large bulb and shattered the tube. 
In No. 42 a crack only occurred in 
the small bulb, either through some 
pre-existing imperfection in the glass 
or from the pressure. When the 
pressure became extreme, the crack 
yielded a little, and the sea-water was 
gradually forced in, driving the con- 
tents of the thermometer before it, 
and, taking it at a disadvantage from 
within, breaking the shell of the large 
bulb, which was unsupported on ac- 
count of the belt of rarefied vapor 
between it and its outer shell. The 
pressure was now equalized within 
and without the instrument, and the 
injury went no farther. Alcohol, cre- 
