(140 ) 
in the spiral Z of the regenerator (Comm. N°. 14 § 3), whence it 
flows through the condensing tube and a cock to the eryostat 
which is indicated only diagrammatically, but may be understood 
from Plate I together with § 2; the evaporated gas escapes through 
the dust-box Yj to the sucking-side of the pump, which communi- 
cates with the gas-sacks G, and G,, into which also the gas from 
the condensor escapes through Z3. The cocks indicated in these 
conduits are required to cut off and to test the separate apparatus. 
Besides the possibility of closing these we should be able to shut off 
the gas-sacks Gj and G, and to stop the Brotherhood. Therefore a 
safety-tube has been connected to the tube conducting the gas. The 
observer, who regulates the influx of liquefied gas by means of the 
observing glasses of the cryostat, keeps in view at the same time 
the vacuum-manometer. The entire cycle could be operated in the 
experiments of Dr. HASENOEHRL, where only a beaker containing 
°/,4 Litre had to be kept full, with about 2 kg. of N,O, which 
was admitted into the apparatus through the cock 4, (Plate III) from 
a reservoir of compressed nitrous-oxide. 
With the first experiments little care was bestowed upon the 
exhausting ete, and therefore a mixture of N,O and air circulated. 
A remarkable phenomenon then occurred. While the observer looked 
through the observing glass at the jet, the jetcatcher was suddenly 
obscured by solid substance, and thick flakes of snow and accumu- 
lated snow heaps rushed down into the beaker B, (PI. I), where 
they took some time to melt. 
This singular phenomenon, for a moment suggesting the doubt 
as to whether something had gone wrong with the P,O,; or the 
circulation of water, could be simply explained as follows. From a 
mixture of N20 and air a liquid phase is separated, which contains 
chiefly N.O, the gas available in the cycle becomes then very 
impure N,O. In the methylehloride refrigerator this on a sufficient 
increase of the pressure is condensed into a solution containing 
much air, which on being poured out sets free the air ina gaseous 
phase in which the partial pressure of the nitrous-oxide is less than 
that of solid nitrous-oxide, so that the liquid phase, consisting 
almost solely of pure uitrous-oxide, congeals. 
Physics. — “The dielectric constants of liquid nitrous oxide and 
oxygen.’ By Dr. Fritz HASENOEHRL. (Communicated by 
Prof. H. KAMERLINGH ONNES). 
(Will be published in the Proceedings of the next meeting). 
