^a 



8 Prof. H. E. Armstrong on Low-Temperature Research 



The results showed that the presence of certain finely divided soHds 

 — silica, charcoal, lampblack — increased the heat insulating power of 

 the vessel, although in presence of air they facilitate the transference 

 of heat. In no case was the solid so effective as a high vacuum 

 alone, the glass surfaces being silvered. 



Photographic action at low temperatures was again referred to in 

 these lectures and shown to be greatly reduced but the caveat at the 

 end of the report should be noted : — 



"It would seem probable that if the plate could be developed at 

 these low temperatures no action would be apparent and that it is 

 during the heating up after the low- temperature exposure that the 

 photographic action on the film takes place through an internal phos- 

 phorescence. This possibility must make us cautious in drawing 

 inferences as to possible chemical action at low temperatures." 



Liquid hydrogen was considered in the lecture on January 20, 1899. 

 The report is of importance on account of the historical matter it 

 contains, particularly the denial of the accuracy of statements put 

 forward by Prof. Ramsay as to the work of the Polish observer, 

 Olszewski. 



In his Commemoration lecture on June 7, 1899, after quoting 

 Davy's remark : — 



" Nothing tends so much to the advancement of knowledge as the 

 application of a new instrument. The native intellectual powers of 

 man in different times are not so much the causes of the different 

 success of their labours as the peculiar nature of the means and 

 artificial resources in their possession," 



Prof. Dewar said : — 



" The new instrument of research, which, for the first time, we 

 have to experiment with before an audience, is the liquid form of the 

 old inflammable air of Cavendish." 



A wonderful series of demonstrations was given in this memor- 

 able lecture, which Lord Kelvin subsequently spoke of as " brilliant, 

 beautiful and splendidly interesting." The liquefaction of the gas, 

 as the lecturer said, was the culmination of ten years of devotion to 

 low-temperature research. By it all doubt was laid at rest as to the 

 true nature of hydrogen : whether it should be ranked with the 

 metals, as Faraday, Dumas and Graham had anticipated it would he 

 eventually — though it must be confessed that the properties of the 

 hydrocarbons are in no way to be taken as in harmony with such a 

 view. 



Solid hydrogen was the subject of the next lecture, on April 6, 

 1900. It was seen to have the appearance of pure ice. Miss Clerke 

 has dealt with this achievement. 



A broad outline of the progress made during the century in 

 studying the properties of gases was given on January 18, 1910 



