SCIENTIFIC SUMMARY. 
99 
striking character of the species of Megarrhiza, had already made consider- 
able progress. The plumule issued from a cleft at the base of the seeming 
radicle, through which a considerable amount of the nutriment stored in the 
cotyledons must have been carried down to assist the growth of the root 
and plumule. From further investigation it appeared that the supposed 
radicle was really formed by two connate petioles of the cotyledons, not 
present in the seed. 
CHEMISTRY. 
Liquefaction of Nitric Oxide, Marsh Gas, and Oxygen . — The close of last 
year will be remembered as the occasion of the announcement of two 
important discoveries in physical chemistry. Oailletet has succeeded in lique- 
fying nitric oxide. This gas which, it had previously been found, would not 
change its state of aggregation if cooled to — 110° C. or subjected to a pressure 
of 50 atmospheres (“ Compt. rend.” 1877, p. 1016), becomes liquid under a 
pressure of 104 atmospheres at — 11° 0. He finds, moreover, that at 8° C. 
the dioxide remains gaseous under pressures equal to 270 atmospheres. 
Berthelot submitted some gases to a pressure of 800 atmospheres without 
inducing a change. The cause of this has been explained by Andrews, who 
has traced the connection which exists between the properties of a so-called 
permanent gas and those of liquids which condense almost without change 
of volume. He finds that for each vapour there exists a critical point of 
temperature, above which the vapour cannot be converted into a liquid by 
any pressure however great it may be. Oailletet also communicates some 
interesting results of experiments made for the purpose of liquefying marsh 
gas. He noticed that at a temperature of 7° O. and under a pressure 
o*f 180 atmospheres the gas under examination becomes cloudy and exhibits 
the same appearance as has been observed in the case of liquid carbonic acid 
when the pressure has been suddenly reduced. There appears little doubt 
that this was condensed marsh gas, which rapidly evaporated when it came 
in contact with the glass and mercury of the apparatus. It is not at all im- 
probable, therefore, that Oailletet will before long succeed in removing light 
carburetted hydrogen from the list of permanent gases. The 11 Journal de 
Geneve ” of the 23rd December (see the u Times,” 26th December, 1877), 
announces the liquefaction of oxygen by Raoul Pictet. The process adopted 
appears, from the short extract referred to, to have consisted in subjecting 
the gas to great pressure and a low temperature produced by the evaporation 
of solid carbonic acid. The latter gas was first liquefied at a temperature of 
— 65° 0. and under a pressure of from four to six atmospheres by the aid of 
sulphurous acid. The carbonic acid was then placed in a long tube con- 
nected with two pumps acting together, and the exhaustion continued till the 
acid became solid. ^Through this tube containing the frozen gas, passed 
another of very fine bore, along which a current of oxygen, prepared from 
potassium chlorate, was conveyed. The pressures to which the oxygen could 
be subjected reached as high as 800 atmospheres. At a pressure, however, 
which it is stated did not exceed 300 atmospheres, the gas was liquefied, and 
a jet of liquid oxygen was projected from the extremity of the fine tube at 
h 2 
