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adopted was not, however, sufficiently new to be worth consider- 
ing here. He succeeded in obtaining a temperature of —200° C. 
In 1887 he solidified air, a nitrogen jelly, containing liquid 
oxygen. The first ounce is said to have cost £600, afterwards 
decreased to £100 per pint. In Lancashire it appears to cost 
about £2 2s. a quart. Nothing has been of greater use in the 
manipulation of these liquid gases than the invention of the Dewar 
vacuum flask, in which liquid air can be kept for many hours. 
Although in 1886 Dewar had prepared a considerable quantity of 
liquid air, and one might have thought that perfection had been 
obtained as nearly as possible in this direction, ten years later 
the method of liquefaction was completely changed. A new 
method was discovered, which needed no preliminary cooling of 
the gases to be liquefied.” 
The Lecturer then entered into a description of Linde’s and 
Hampson’s apparatus for the manufacture of liquid air, which, 
by the utilisation of mechanical power, is capable of liquefying 
an unlimited amount of air without the use of auxiliary re- 
frigerants. He then proceeded— 
‘But what is the use of liquefied gases? At the present 
time, tons of liquid carbon dioxide are used by the manufacturers 
of aerated waters ; liquid sulphur dioxide is an ordinary article 
of commerce, and is used for bleaching in certain cases. Liquid 
nitrovs oxide is used in small surgical operations. Refrigerating 
machines, which are to be found in most towns, are the outcome 
of researches in low temperatures. Possibly in the near future, 
liquid air will be the refrigerating ageut. Hach hotel and 
hospital will be able to have its own plant, so that it will be as 
easy to have a cold room in summer as a warm one in winter. 
Our American friends proposed to use liquid gases for working 
machinery, but nothing of a practical character has been done 
yet. The very low temperature obtained by the expansion of 
these liquids is objectionable. It is not impossible to use 
it, but it is not likely to be used where steam is available. Only 
a few days ago Dr. Macfadyen read a paper before the Royal 
Society, in which he described a method of attacking typhoid 
fever by means of liquid air. He has been able to separate the 
toxie juices developed by the typhoid bacterium when living, from 
the living bacterium itself. From this he had been able to pre- 
pare a serum which is said to be both preventtive and curative. 
« Although so much has been done in the last thirty years, 
there is as ample room for investigation as when Faraday com- 
menced his researches eighty years ago.” 
During the course of the lecture Mr. Stevens exhibited the 
properties of air in its gaseous and liquid forms, and was ably 
assisted in many interesting experiments by Mr. J. W, Bell, 
