316 



SCIENCE 



[N. S. Vol. XXVIII. No. 714 



of " Interesting Animal Surgery " is noted an 

 operation for cataract performed on the In- 

 dian rhinoceros, "Mogul." A Census of 

 American Bison gives a total of only 2,047 on 

 January 1, of which 969 were in captivity in 

 the United States and 41 in Canada: these 

 figures are now different owing to the sale to 

 Canada of the Pablo herd. As a supplement 

 to the bulletin F. A. Lucas has an article on 

 " The Passing of the Whale," noting that the 

 number of whales are being rapidly lessened 

 and that unless protective measures are taken 

 one or two species are in danger of actual ex- 

 termination. 



Bird-Lore for July-August contains articles 

 on "The Fish Hawks of Gardiner's Island," 

 by Prank M. Chapman ; " The Eeturn of the 

 Snowy Heron," by Herbert R. Sass ; " A Little 

 Blue Heron Rookery," by M. Harry Moore, 

 and the fifth paper on " The Migration of 

 Flycatchers," by W. W. Cooke. The Educa- 

 tional Leaflet is by Mabel Osgood "Wright and 

 devoted to the tree swallow. The report on 

 The Audubon Societies notes steady progress, 

 but as the result of continuous work, and the 

 vast numbers of birds sold for " plumes " 

 shows the necessity of further hard work. 



THE LIQUEFACTION OF HELIUM^ 

 In his communication to the Amsterdam 

 Academy concerning the liquefaction of 

 helium Professor Onnes describes in consid- 

 erable detail the steps that led up to that 

 achievement, the complicated apparatus em- 

 ployed, and the difficulties that had to be sur- 

 mounted. The narrative conveys a vivid 

 impression of the obstacles that have to be 

 overcome in order to lower temperature a very 

 few degrees in the neighborhood of the zero of 

 absolute temperature. In spite of the most 

 elaborate and comprehensive preparation and 

 ample supplies of liquid hydrogen, not only 

 was the whole apparatus, with its subsidiary 

 arrangements, tested to its utmost capacity, 

 but the physical energies of the professor and 

 his assistants were well-nigh exhausted by 

 the prolonged struggle. 



The constants of helium, while showing 

 ' From the London Times. 



some important points of difference, are 

 found to agree very remarkably with the pre- 

 dictions made by Dewar on theoretical 

 grounds in his presidential address to the 

 British Association in 1902. After a correc- 

 tion of two tenths of a degree the boiling 

 point of the liquid is found to be 4.5 degrees 

 Centigrade. By exhaustion to below one 

 centimeter, and probably below seven milli- 

 meters of pressure, the professor considers 

 that the temperature was reduced to about 3 

 degrees without, however, affecting the mobil- 

 ity of the liquid. 



The density of the liquid helium is 0.15, or 

 about double that of liquid hydrogen; and 

 the proportion between the density of the 

 vapor and that of the liquid is as 1 to 11. 

 The critical pressure is in the neighborhood 

 of two or three atmospheres, which is rela- 

 tively low in comparison with the figures for 

 other gases. 



Professor Onnes deduces a critical temper- 

 ature not much higher than 5 degrees Centi- 

 grade. But with regard to this and all the 

 other figures he says that more careful meas- 

 urements and calculations must be made be- 

 fore any certain and final conclusion can be 

 reached. At temperatures so near to the ab- 

 solute zero there is always room for doubt in 

 the application of laws deduced from the be- 

 havior of bodies in more normal conditions, 

 and for the present we must apparently be 

 content to accept the values of the helium 

 constants as provisional. 



SPECIAL ARTICLES 



A NEAV GROUP OF PERMIAN AMPHIBIANS 



More than thirty years ago the late Pro- 

 fessor Cope described from the reputed 

 Permian, of Illinois, three small vertebrae 

 which he considered reptilian and which he 

 made the type of the genus and species 

 Lysorophus tricarinatus. Six years ago Pro- 

 fessor Case recognized in certain material — a 

 considerable series of connected and more or 

 less intertwined vertebrse — which he had col- 

 lected from the Permian of Texas, the same 

 genus, and, possibly, the same species. He 

 reached the conclusion that the animal was 



