June 24, 1898.] 



SCIENCE. 



855 



increase of 24, and five of these bad passed be- 

 fore the Committee and received diplomas, one 

 of them being a lieutenant in the navy. 

 Among the pupils there were 2G civilians, 24 

 officers of the army and navy, four in the co- 

 lonial service, four civil engineers and two mis- 

 sionaries. The Society owes much to Mr. 

 Coles for the pains and trouble he had taken, 

 and for the time he had devoted to the work of 

 teaching. This year the Society had reached 

 and passed the four thousandth figure in the 

 number of its Fellows. This was a landmark 

 in their progress, while the most notable events 

 in their history this year were the grant of 

 diplomas and the creation of a growing number 

 of trained scientific explorers. 



LIQUID HYDROGEN. 



At the meeting of the Loudon Chemical So- 

 ciety on June 2d Professor Dewar gave a short 

 account of the first attempts made to deter- 

 mine the physical constants of liquid hydrogen. 

 Among the most interesting points brought 

 forward, according to the report in the London 

 Times, was that just as in the middle of the last 

 century chemists were startled by Cavendish's 

 discovery of a factitious gas, namely, hydrogen, 

 having a density one-fourteenth that of air, so 

 now they were startled by finding in liquid 

 hydrogen a liquid having a density of 0.07, or 

 roughly one-fourteenth that of water. Hydro- 

 gen occluded in palladium has been found to 

 have a density of 0.62. "Whatever, therefore, 

 be the form in which it exists in that metal it is 

 more than eight times denser than in the liquid 

 condition, and consequently must be in a state 

 of chemical combination, and not merely in 

 one of liquefaction. Liquid hydrogen is thus 

 by far the most extraordinary liquid known. 

 The lightest liquid hitherto obtained is liquid 

 marsh-gas, which has at its boiling-point a 

 density of about two-fifths that of water. 

 Liquid hydrogen, therefore, has only one-sixth 

 of the density of liquid marsh -gas, and the sur- 

 prising thing is that having such a small density 

 it is so well defined, so easily seen, and so ca- 

 pable of collection and manipulation in vacuum 

 vessels. 



Professor Dewar has determined the boiling- 

 point of the liquid by means of a platinum resist- 



ance thermometer — practically the only form, 

 available at such low temperatures. The re- 

 sult he has obtained is — 238° C. at atmos- 

 pheric pressure ; in other words, liquid hydro- 

 gen boils steadily at 35° above the zero of 

 absolute temperature. From all analogy it i& 

 inferred that the lowering of temperature that 

 will be produced by forcing the liquid to boil in 

 vacuo cannot amount to more than 10 or 15°. 

 It is, therefore, possible to say with confidence 

 that at the present moment science can project 

 no method that will get nearer to the absolute 

 zero than 20 or 25°. 



The boiling-point of liquid hydrogen is really 

 higher than suggested by theory and the work 

 of other experimenters. The density of the- 

 vapor coming oif from the boiling liquid is 

 eight times denser than the gas at ordinary 

 temperatures, whereas in the case of liquid air 

 the vapor is only^four times heavier. Liquid 

 hydrogen again is 100 times denser than the 

 vapor it is giving off, whereas the density of 

 liquid oxygen is 255 times greater than that of 

 its vapor. The atomic volume of liquid hydro- 

 gen at its boiling point is 14.3, while that of 

 oxygen is 13.7. 



It may be mentioned that the platinum resist- 

 ance thermometer when immersed in the liquid 

 hydrogen is cooled to within six platinum de- 

 grees of its zero point, so that if cooled these 

 few degrees more — as it can be by means of the 

 liquid boiling under reduced pressure — it must 

 break down, becoming an infinite conductor 

 with no resistance. 



GENERAL. 



Boston University has conferred the degree 

 of LL.D. on Alpheus Hyatt, professor of zoology 

 and paleontology in the University. 



Professor W. M. Davis and Professor E. L. 

 Mark will take advantage of the sabbatical 

 year allowed by Harvard University to spend 

 the period in study and research abroad, while 

 Professor W. Gr. Farlow will spend the winter 

 in the West Indies. Professor H. F. Osboru, of 

 Columbia University, is also enjoying a sabbat- 

 ical year and is at present abroad. 



The Loubat prizes of Columbia University, 

 awarded every fifth year, alternately for works 

 on the history, geography and numismatics of 



