oe, 
structure of this membrane shows much evidence in favour of 
this theory. Its fibres are taut and of gradually increasing length, 
whereas longitudinally the membrane is not under tension. More- 
over Hemholtz’s view that the high notes are perceived in the 
lower and low notes in the upper portion is supported by evidence 
from actual patients whose internal ears have been examined 
after death. Some difficulties in the acceptation of this theory 
of Hemholtz have lately been disposed of by Dr. Albert Gray, 
into which matter Mr. Yearsley entered at considerable length. 
Dr. Gray’s modifications of the theory are based on the principle 
of maximum stimulation, and seem to account satisfactorily for 
the facts. 
Friday, March, 6th, Mr. P. E. Vizard, Vice-President, in the 
chair. 
Dr. J. F. Spencer, D.Sc., Ph.D., gave a lecture on ‘* The 
Liquefaction of Gases.’’ The lecturer detailed the history of 
the science of liquefaction. In 1823, Faraday, at the request of 
Sir Humphry Davy, investigated the action of heat on chlorine 
hydrate. He succeeded in liquefying chlorine, sulphur, dioxide, 
sulphuretted hydrogen, carbonic acid gas, nitrous oxide (laughing 
gas), cyanogen, and ammonia, by liberating these gases in closed 
tubes, the pressure produced by their liberation in the enclosed 
space having been sufficient to condense them to the liquid state. 
Previous to this work of Faraday success had been claimed by 
Count Rumford and Babbage in the liquefaction of carbon dioxide, 
by Northmore of chlorine, and by Perkins of air ; but later know- 
ledge has shown that these supposed successes were very doubtful 
—indeed, in the case of air, quite impossible. In 1835 Thilorier 
produced a gallon of liquid carbonic acid gas by pouring vinegar 
on chalk in an iron vessel. On liberating the liquid from its con- 
finement he reduced its temperature so rapidly by evaporation 
that the gas solidified in the form of snow. On one occasion the 
pressure in his producer caused its explosion, and resulted in the 
death of his assistant. Up to this time great danger had generally 
attended these investigators, who had worked in an atmosphere 
of flying fragments of apparatus. 
Between 1861 and 1870 the work of Andrews threw light on 
the proper methods of liquefying gases. He showed that for 
each gas there is a temperature, named by him the “critical 
temperature,’ above which no amount of pressure will result in 
liquefaction, and that the so-called ‘‘ permanent ” gases required 
