British Aseveiation. 295 
during the last year. This was followed by a report on the manufactures 
of the South Lancashire District, by Professor H. E. Roscoe, Dr Schunck, 
and Dr Angus Smith. Dr Andrews then read a paper ‘‘ On the Effects of 
Great Pressures combined with Cold, on the Six Non-condensible Gases.”’ 
The gases, when compressed, were always obtained in the capillary end 
of thick glass tubes, so that any change they might undergo could he 
observed. In his earlier experiments the author employed the elastic 
force of the gases evolved in the electrolysis of water as the compressing 
agent, and in this way he actually succeeded in reducing oxygen gas to 
1-300th of its volume at the ordinary pressure of the atmosphere. He 
afterwards succeeded in effecting the same object by mechanical means, 
and exhibited to the Section an apparatus by means of which he had been 
able to apply pressures, which were only limited by the capability of the 
capillary glass tubes to resist them ; and while thus compressed the gases 
were exposed to the cold attained by the carbonic acid and ether bath. 
Atmospheric air was compressed by pressure alone to 3}; of its original 
volume and by the united action of pressure and a cold of 106° Fahr. to 
1-675th ; in which state its density was little inferior to that of water. 
Oxygen gas was reduced by pressure to 1-324th of its volume, and by 
pressure and cold to 1-554th ; hydrogen by the united action of cold and 
pressure, to 1-500th ; carbonic oxide, by pressure, to 1-278th—by pressure 
and cold to 1-278th; nitric oxide, by pressure to 1-310th, by pressure 
and a cold of 160° Fahr. to 1-680th. None of the gases exhibited any 
appearence of liquefaction even in these high states of condensation. The 
amount of contraction was nearly proportional to the force employed, till 
the gases were reduced to from about 1-300th to 1-350th of their volume ; 
but, beyond that point, they underwent little further diminution of 
volume from increase of pressure. Hydrogen and carbonic oxide appear 
to resist the action of pressure better than oxygen or nitric oxide. The 
paper of Dr Andrews was followed by one ‘on the Thermal Effects of 
Elastic Fluids,” by Dr Joule and Professor W. Thomson. 
On Friday the President exhibited some photographs of different 
Spectra, and read a paper on the subject.—The apparatus by which the 
spectra may be photographed consists of an ordinary camera obscura 
attached to the end of a long wooden tude, which opens into a cylindrical 
box, within which is a prism glass, or a hollow prism filled with bisul- 
phide of carbon. Ifthe prism be so adjusted as to throw the solar rays, 
reflected from a heliostat, upon the screen of the camera and the wires 
which transmit the sparks from a Ruhmkoffer coil are placed in front of 
the uncovered portion of the slit, the two spectra are simultaneously im- 
pressed. The solar beam is easily intercepted at the proper time by 
means of a small screen, aud the electric spectrum is allowed to continue 
its action for two or three, or six minutes, as may be necessary. He did 
not find that anything was gained in distinctness by interposing a lens of 
short focus between the slit and the wire which supplied the sparks, with 
the view of rendering the rays of the electric light parallel like those of 
the sun, owing to the absorbent action of the glass weakening the photo- 
graphic effect ; and the flickering motion of the sparks being magnified 
by the lens, rendered the lines less distinct than when the lens was not 
used, Although with each of the metals (including platinum, gold, silver, 
copper, zinc, aluminum, magnesium, iron), when the spark was taken in 
air, he obtained decided photographs, it appeared that in each case the 
impressed spectrum was very nearly the same, proving that few of the 
lines produced were those which were characteristic of the metal. The 
peculiar lines of the metal seemed chiefly to be confined to the visible 
portion of the spectrum, and these had little or no photographic power. 
This was singularly exemplified by repeating the experiment upon the 
