134 Professor Deivar [Marcli 27, 



Detailed drawings of the Royal Institution refrigerating plant now 

 in use have not been published, simply because changes are constantly 

 being made in the apparatus. Science derives no benefit from the 

 description of transitional apparatus when there is no secret about 

 the working process and how to carry it into effect. The Phil. Mag. 

 of February, 1895, contains a fantastic claim put forward by Professor 

 Olszewski, of Cracow, that because he used in 1890 a steel tube com- 

 bined with a stopcock to draw off liquid oxygen, he had taught the 

 world, to use his own language, " the method of getting large 

 quantities of liquid gases." In addition the Professor alleges, four 

 years after the event, that the experiments made at the Royal Insti- 

 tution are chiefly borrowed from Cracow, and that he is entitled to 

 the credit of all low temperature research. As to such chiims, one 

 can only wonder at the meagre additions to knowledge that in our 

 time are unhesitatingly brought forward as original, and more 

 especially that scientific men could be got to give them any currency 

 in this country. Such persons should read the late Professor Wro- 

 blewski's pamphlet, entitled ' Comment I'air a ete liquetie,'* and 

 make themselves generally acquainted with the work of this most 

 remarkable man before coming to hasty conclusions on claims of 

 priority brought forward by his some time colleague. 



Liquefying Apimratus. — A laboratory apparatus for the production 

 of liquid oxygen and other gases is represented in section (Fig. 1). 

 "With this simple machine, 100 c.c. of liquid oxygen can readily be 

 obtained, the cooling agent being carbon dioxide, at the temperature 

 of —79°. If liquid air has to be made by this apparatus, then the 

 carbon'c acid must be kept under exhaustion of about 1 inch of mer- 

 cury pressure, so as to begin with a temperature of— 115°. Under 

 such conditions the yield of the liquid gases is much greater. The 

 gaseous oxygen, cooled before expansion by passing through a spiral 

 of copper tube immersed in solid carbon dioxide, passes through a 

 fine screw stopcock under a pressure of 100 atmos., and thence back- 

 wards over the coils of pipe. The liquid oxygen begins to drop in 

 about a quarter of an hour from starting. The general arrangement 

 of the circuits will be easily understood from the se-tional drawing. 

 The pressure in the oxygen cylinders at starting is generally about 

 150 atmos., and the best results are got by working down to about 

 100. If a small compressor is combined with the apparatus the 

 liquefaction can go on continuously. This little apparatus will enable 

 liquid oxygen or air to be used for demonstration and research in all 

 laboratories. 



Vacuum Vessels. — It has been shown in previous papers t that a 

 good exhaustion reduces the influx of heat to one-fifth part of what is 

 conveyed when the annular space in such double-walled vacuum 

 vessels is filled with air. If the interior walls are silvered, or excess 



* Pfiris, Libraire du Luxembourg, 1885. 



t " On Liquid Atmospheric Air," Proc. Roy. Inst. 1893; "Scientific Uses of 

 Liquid Air," ibid. 1894. 



