360 
PROFESSOR A. M. WORTHINGTON ON THE 
electric storage cell, and the other could at pleasure be touched by the bare end of a 
similar stout wire from the other pole. By this means the fine platinum wire could 
be heated suddenly to redness, when the liquid which was tugging at it immediately 
let go its hold. The bubble of vapour thus caused to appear had its upper end at the 
wire, and extended below to a distance along the fine tube, which could be accurately 
measured against a scale placed, to avoid parallax, on a mirror behind the tube. 
The relation of the bore of the tube to the whole internal volume of the apparatus 
had been previously ascertained, and thus the fraction of the whole volume which the 
extension represents was known. 
This extension is, however, only apparent, and it is necessary to determine and to 
subtract from it the amount by which the volume of the containing vessel has been 
diminished by the inward pull. The separate operation for determining this correc¬ 
tion will be described later. I shall now explain the mode of filling and sealing the 
apparatus, and of conducting an experiment, with the precautions and minor correc¬ 
tions necessary for securing good measures of the extension. 
Fig. 2. 
After thoroughly cleaning the apparatus with, first, a solution of potassium hydrate, 
then dilute hydrochloric acid, and then finally with distilled water, it is sealed at E 
to a second glass bulb HK, with arms HE, KLM, as shown in fig. 2. 
