140 
Proceedings of the Royal Society 
with danger, were it necessary to be in its neighbourhood, it 
occurred to me that an automatic arrangement might be employed 
to give notice that the temperature had been reached to which it 
was intended to subject the digester. 
For this purpose I employed a thermometer with a somewhat 
wide tube and large bulb. A platinum wire is sealed into the 
bulb, and touches the mercury, whilst a brass wire passes down 
the tube, and is held in position by a binding screw. The two 
wires are connected with an electric bell, the brass wire being so 
adjusted, that when a particular temperature is reached the mer- 
cury touches its end, and thus completes the circuit, and causes the 
bell to ring. 
In order to test the digester, about 200 grammes of a mix- 
ture of two-parts bromine and three of acetic acid was placed 
in it, and after fixing it in its frame, the whole apparatus was 
immersed in an oil bath and heated to 150° C., the temperature 
at which reaction in this case takes place. The experiment was 
made in a cellar, and the bell placed in a room some distance 
off. The gas to heat the oil bath was led by a tube from another 
cellar, so that it could be regulated without going near the digester. 
In about an hour and a half the bell rung, and thereupon the gas 
was shut off; and on examining the digester next day, it was 
found that the reaction had taken place, and that only twelve 
grammes of product had been lost — a very inconsiderable quantity. 
As the action of bromine on acetic acid is very sudden, and 
accompanied by the disengagement of a large volume of hydro- 
bromic acid, the apparatus may be considered to have undergone a 
very severe test, and that its efficacy for all ordinary purposes is 
established. 
Should the digester come into general use, it will certainly save 
chemists much time and labour. 
The following Gentlemen were elected Fellows of the 
Society : — 
Rev. Francis Le Grix White, M.A. 
James Duncan, Esq., Benmore. 
Rev. Norman Macleod. 
J. S. Fleming, Esq. 
James Douglas H. Dickson, M.A. Glasg., B.A. Camh. 
