STUDY OF OXYGEN AT LOW PRESSURES. 79 
not, however, think that native gold has necessarily been in a 
fused condition, on the contrary I think it has been deposited 
from solution and usually within veins or pockets in rocks, 
although if it had been deposited round nuclei, it might still have 
possessed the crystalline structure which has been described and 
figured in this paper. 
A CONTRIBUTION to tae STUDY or OXYGEN ar 
| LOW PRESSURES. 
By R. Taretrant, m.a., Professor of Physics in the University 
of Sydney, and Frorence Martin. 
[Read before the Royal Society of N. S. Wales, June 2, 1897.] 
WHEN a mass of oxygen is enclosed in a tube and the mercury 
Pressure on it continuously diminished, it is found that at about 
07 mm., and over a certain range of lower pressures, the gas 
“ppears to undergo a change of condition. The phenomenon 
may be described in the words of Bohr, its discoverer, “A 
given mass of oxygen is enclosed in a tube and the mercury 
adjusted so as to give rise to a pressure rather less than 
07mm. If the volume of the gas is now reduced by raising 
the pressure, say to 0-8 mm., it is noted that this pressure will 
not remain constant ; but varies more or less with lapse of time. 
* three to five hours the pressure will fall by some 12% of its 
initial value (the volume being constant). After five hours the 
Pressure was found to have attained its steady value, so far as 
observations extending over twenty-four to thirty-six hours could 
determine.” 
This curious behaviour of oxygen was also noted by Baly and 
Ramsay,’ who observed that at a pressure of about 0°75 mm. 
1 Wied. Ann. 27, p. 475. 2 Phil. Mag., 38, p. 324, 1894. 
