414 
]\[ESSRS. T. E. THORPE AND J. W. RODGER ON THE RELATIONS 
below that of the bottom of the air reservoir. After water has siphoned over from L 
to R, and the air in the former has thus been reduced to atmospheric pressure, the 
cock Q is turned to prevent unnecessary absorption of water from L by the acid 
in M. 
In front of the bath is placed the iron stand S, which is fitted with levelling screws 
and rests on the low wooden support shown. Fixed to the stand are three vertical 
brass rods each carrying a telescope. The telescope on the middle rod is used for 
reading the thermometer T. The telescope on the rod to the right of the middle rod 
is used for viewing the marks m^, on the right limb of the gl is chrome ter, that on 
the rod on the left for the marks on the left limb. On these outer rods are fitted the 
stops U, U, which have been so placed that, after levelling the stand S, when a 
telescope and a stop are in contact, one of the marks in of the glischrometer is in the 
field of view. The stop-watch is kept on the table just to the right of the telescope 
support. 
To obtain observations at temperatures above that of the atmosphere, the bath is 
heated by Bunsen burners, which are protected from draughts by a zinc screen fitted 
with glass windows, in order that the flames may be seen. The gas supply is regulated 
by a cjuadrant tap. A, fixed to the side of the table close to the observer’s hand. 
Temperatures below that of the atmosphere are obtained by introducing fragments of 
ice into the outer compartment of the bath, this compartment being kept uncovered by 
the lids at such times. 
The double bath not only tends to keep the liquid round the glischrometer of a more 
uniform temperature, but it also has the advantage that the liquid in the inner com¬ 
partment need not be renewed very frequently, as any dust or dirt introduced while 
regulating the temperature is confined to the outer compartment, and thus in no way 
interferes with the telescope readings. 
Method oe Expeeiment. 
Before introducing the liquid to be examined, it was essential that the glischrometer 
should be perfectly clean and dry. The instrument was first rinsed out by successive 
cjuantities of dust-free water, alcohol, and ethei’, or, under ordinary circumstances, 
alcohol and ether only, and allowed to drain. It was then transferred to a specially 
constructed air-bath, heated to about 80° or 100°, and a current of air, filtered through 
cotton wool, and dried by oil of vitriol, was drawn through it for some time. 
The liquids used for washing were obtained dust-free by distillation in an appa¬ 
ratus made entirely of glass, consisting of a large Wurtz flask, fitted with a 
well-ground glass stopper, the exit tube being sealed to a glass tube, which was 
passed through a Liebig’s condenser. They were stored in ether bottles which, 
in addition to well-fitting glass stoppers, had glass caps ground on to their necks. 
The liquid is gently distilled in this apparatus and, after sufficient time has been 
