764 Prof. H. E. Armstrong on Low-Temperature Research ; 



interieur. L'enveloppe annulaire, ou le vide sec existe, constitue la 

 parol thermo-isolatrice. — J'ai pu constater dans certaines cas qu'iin 

 liquide chaud place dans le vase interieur se refroidit de quinz a vingt 

 fois plus lentement que si Tenveloppe isolatrice n'existait pas." 



Such vessels apparently could not then be made in France (cf. 

 Claude, p. 216) any more than in England ! But had they been 

 made as described by D'Arsonval, they would have been far inferior, 

 through lack of the highly-polished silvered interior which is an 

 essential feature of the Dewar vessel. 



Sir James Dewar, who was not aware of these French publications 

 on the subject when I brought them under his notice a year or so 

 ago, was able to develop the construction of glass vacuum vessels but 

 slowly owing to the difficulties of glass-blowing and the absence from 

 this country of competent makers willing to undertake their construc- 

 tion. The use of such vessels only became possible from 1898 

 onwards, after he had succeeded in getting them made in Germany. 

 Meanwhile, the manufacture of such vessels has been developed into an 

 important industry in that country, especially since their introduc- 

 tion in the form of the all-familiar Thermos Flask. Having enjoyed 

 a world monopoly, even up to the outbreak of war, the Germans have 

 profited greatly from the manufacture. 



Sir James Dewar alone has the credit of having made them the 

 perfect and indispensable weapons of low-temperature research they 

 now are ; without them the more serious and important part of the 

 work could not have been accomplished. In the 1914 lecture, it 

 was pointed out that they were equally useful in storing hot liquids. 

 "When the production of vacuum vessels from quartz instead of glass 

 is perfected, it is to be expected that they will come largely into 

 use in preventing the escape of heat. Xo advantage arises from 

 silvering such vessels, but if coated with nickel deposited from nickel 

 carbonyl they can be exposed to high temperatures. 



The later invention of the metallic vacuum vessel — which has. 

 been rendered possible only through the discovery of the marvellous 

 condensing power of charcoal at very low temperatures — is one that 

 eventually, in all probability, will rank even beyond that of the 

 fragile glass vessel in importance, in view of its many practical 

 appHcations. In this vessel, the promise of the brass vacuum calori- 

 meter of 1873 is entirely fulfilled. One use to which it is being 

 put in the war, primarily by the Germans, is as a means of providing* 

 artificial respiration for aeroplane pilots and observers when flying at 

 great heights. 



The various forms given to the vacuum vessel are described and 

 figured ill lectures delivered on January 18, 1901, and January 23, 1914. 



But from his many inventions, the inventor himself has had no 

 profit : as Samuel Butler remarks, " If genius cannot be bought with 

 money, still less can it sell what it produces. . . ." 



