140 Proceedings of Boy al Society of Edinburgh. [sess. 
Each experiment was carried out in detail as follows : — One end 
of a short length of thin glass tube, T, was closed and then sealed 
to a very small glass bulb, B. Near the point of attachment there 
were, on opposite sides, two oval-shaped openings in the bulb. 
The glass tube was free to move up 
and down through one of two holes 
bored through a very short common 
cork, C, the downward movement 
being prevented from exceeding six 
centimetres by a knob in the upper 
part of the glass tube. Special care 
being taken to see that the bulb was 
clean and dry, it was drawn down 
from the cork about six centimetres 
and the cork fixed in a clamp. The 
filings ('5 gramme was the quantity 
always used in each of the brass and 
copper and zinc experiments) were 
then most carefully inserted into the 
bottom of the bulb by one of the open- 
ings, and the bulb was then drawn up 
close to the cork. Through the other 
hole in the cork a very thin, sensitive, 
short-range thermometer, M, whose 
marked divisions correspond to '05° 
C., was passed. The cork carrying 
the bulb and attached tube and ther- 
mometer was then carefully fixed in 
the neck of a small flask, F, of thin 
glass containing the nitric acid, 60 
cubic centimetres of which were used 
in every one of these experiments. 
The figure is a representation of the 
arrangements at this stage. Holding 
the flask by the lip with three fingers of one hand, it was gently 
shaken so as to give the acid a rotating motion. In this way the 
flask and contents soon attained a uniform temperature, which was 
very carefully noted, the reading of the thermometer being always 
