Physics. 
421 
1876.] 
* On April 28th Dr. Andrews, F.R.S., delivered a ledure before the 
Chemical Society “ On Certain Methods of Physico-Chemical Research.” The 
ledurer began by describing the simple form of apparatus which he employed 
many years ago in his researches on the heat evolved in the combination of 
oxygen, chlorine, bromine, &c., with other bodies. In every case the bodies 
to be combined were enclosed in a vessel surrounded with water, and the 
combination was effeded either by the ignition of a fine platinum wire, or, 
where they aded diredly upon one another, by the fradure of a glass capsule 
containing one of the combining bodies, the heat being measured by the rise 
of temperature of the water. He next referred to the arrangement by which 
he had been the first to decompose water so as to render visible the hydrogen 
and oxygen, and to measure their relative volumes, by means of atmospheric 
eledricity and of the eledrical currents from the ordinary machine. For this 
purpose fine platinum wires were hermetically sealed into fine thermometer 
tubes, which were then filled with dilute sulphuric acid by withdrawing the 
air by ebullition. The same current of fridional eledricity will decompose 
the water in almost an indefinite number of such couples arranged in a con- 
secutive series. Capillary tubes of this kind may be employed for eudiometric 
experiments, which would be exceedingly tedious in wide tubes. Thus oxygen 
gas can be at once absorbed by passing the silent discharge through it while 
standing over a solution of iodide of potassium. By means of the air-pump it 
is easy, with a gentle exhaustion, to expand the gas so that it may fill the 
whole tube, while the open end is immersed in the liquid which it is desired 
to introduce. On removing the pressure, the gas will be in contad with the 
new liquid. The ledurer exhibited some of the original tubes with which 
Prof. Tait and he first determined that ozone is a condensed form of oxygen, 
and explained a form of apparatus by means of which this important fad can 
be exhibited as a class experiment. A full description of this apparatus will 
be found in his ledure on ozone, which was delivered some time ago before 
the Royal Society of Edinburgh, and has since been published by the Scottish 
Meteorological Society. With this apparatus the ledurer has been able to 
determine that chlorine gas undergoes no change of volume from the prolonged 
adion of the eledrical discharge. His experiments on this subjed have not 
yet been published, but they were made under singularly favourable conditions 
for discovering a very small change of volume in the gas, if any such change 
had occurred. The ledurer, in the next place, briefly alluded to the method 
he formerly employed for determining the latent heat of vapours, of which a 
detailed account was given in a former communication to the Chemical 
Society. The apparatus employed admits of exad experiments being made on 
a small scale, and consequently on substances in an absolutely pure state — an 
objed of even greater importance in enquiries of this kind than in ordinary 
chemical analysis. Pie remarked that a large field for investigations in this 
part of the domain of science lay comparatively uncultivated, and would yield 
a rich harvest of results to any one who would enter upon it. Passing from 
this subjed, the ledurer described a dividing and calibrating machine, which 
he contrived some years ago for the special work in which he has been 
engaged, and which has given to many of his investigations an accuracy 
otherwise hardly obtainable. He has been enabled by means of it to construd 
thermometers whose readings are absolutely coincident throughout every part 
of the scale, and to calibrate with*almost perfed accuracy the glass tubes used 
in his pressure experiments. It would be impossible in an abstrad to describe 
the construdion of this machine, but it may be important to mention that the 
screw which moves the microscope or divider is a short one, of remarkable 
accuracy, construded by Troughton and Simms. The last subjed treated 
was the ledurer’s method of investigating the properties of gaseous and liquid 
bodies at high pressures and under varied temperatures. By means of his 
apparatus, which was exhibited to the meeting, pressures of 500 atmospheres 
can be readily observed and measured in glass tubes — in a word, a complete 
mastery obtained over matter under conditions hitherto beyond the reach of 
dired observations. This has been effeded by a novel mode of packing a fine steel 
screw, so that while entering a confined portion of water no leakage whatever 
