SCIENCE 



EditubiaIi Committee : S. Newcomb, Mathematics ; E. S. Woodward, Mechanics ; E. C. Pickering, 



Astronomy; T. C. Mendenhall, Physics; R. H. Thurston, Engineering; Ira Remsen, Chemistry; 



J. Le Conte, Geology; W. M. Davis, Physiography; Henry F. Osborn, Paleontology; W. K. 



Brooks, C. Hart Merriam, Zoology; S. H. Scuddee, Entomology; C. E. Bbssey, N. L. 



Beitton, Botany; C. S. Minot, Embryology, Histology; H. P. Bowditch, Physiology; 



J. S. Billings, Hygiene; J. McKeen Cattell, Psychology; 



J. W. Powell, Anthropology. 



Fbiday, April 27, 1900. 



CONTENTS: 



Liquid Hydrogen : Peofessoe James Dewae.. 641 



Some Recent Contributions to Terrestrial Magnetism : 

 De. L. a. Bauee 651 



Exotic Mollusca in California : De. Robert E. 

 C. Steaens 655 



Scientific Books : — 



3Xanual and Mechanical Froductivity : Peofes- 

 soe R. H. Thoeston. Le Conte's Comparative 

 Physiology and Morphology of Animals : Pro- 

 fessor J. S. Kingsley. Books Received 659 



Scientific Journals and Articles 663 



Societies and Academies : — 



Tlie National Academy of Sciences. New York 

 Academy ofScieiices, Section of Astronomy, Physics 

 and Chemistry : Dr. Wm. S. Day. Torrey 

 Botanical Club : Professor Edwaed S. Bue- 

 GESS. Science Club of the University of Wiscon- 

 sin : Professor William H. Hobbs. Chem- 

 ical Society of Washington : De. William H. 

 Keug. The Philosophical Society of Washing- 

 ton ; E. D. Peeston 663 



Lifcussion and Correspondence: — 



Bequest for Co-operation in Work on the Coming 

 Solar Eclipse : PROFESSOR R. W. Wood. A 

 Statement regarding the Situation at the Uni- 

 versity of Cincinnati : PROFESSOR THOMAS 

 French, Je. Information Wanted : De. G. 

 V. N. Dearborn. Note on Pigments of the 

 Coccid Ckionaspis furfura, Fitch : PEOFESSOE 

 T. D. A. COCKERELL 667 



Current Notes on Physiography : — ■ 

 PoHo Rico ; The Dunes of Gascony ; The Mor- 

 van ; Tiie Flaming : Peofessoe W. M. Davis 671 



Botanical Notes : — 



Fossil Plants of the Black Hills; Physiological Edle 

 of Mineral Nutrients ; The Forest Reserves of the 

 United States ; A Study of Fungus Poisons ; 

 Professor Charles E. Bessby 672 



The Laboratory of the U. 8. Fish Commission, Beau- 

 fort, N. C: Peofessoe H. V. Wilson 674 



Professor Dewar on Solid Hydrogen 674 



X-Rays and Photographic Plates 675 



Scientific Notes and News 676 



University and Educational Netos 680 



MSS. intended for publication and books, etc., intended 

 for review should be sent to the responsible editor, Profes- 

 sor, J. MoKeen Cattell, Garrison-on-Hudson, N. Y. 



LIQUID HYDROGEN.* 

 From the year 1878, when the experi- 

 ments of Cailletet and Pictet were at- 

 tracting the attention of the scientific 

 world, it became a common habit in text- 

 books to speak of all the permanent 

 gases, without any qualification, as having 

 been liquefied, whereas these experiment- 

 alists, by the production of an instantaneous 

 mist in a glass tube of small bore, or a 

 transitory liquid jet in a gas expanding 

 under high compression into air, had only 

 adduced evidence that sooner or later the 

 static liquid form of all the known gases 

 would be attained. Neither Pictet nor Cail- 

 letet in their experiments ever succeeded 

 in collecting any of the permanent gases in 

 that liquid form for scientific examination. 

 Yet we meet continually in scientific litera- 

 ture with expressions which lead one to be- 

 lieve that they did. For instance, the fol- 

 lowing extract from the ' Proceedings ' of 

 the Eoyal Society, 1878, illustrates this 

 point very well : " This award (Davy 

 Medal) is made to these distinguished men 

 (Cailletet and Pictet) for having independ- 

 ently and contemporaneously liquefied the 

 whole of the gases hitherto called perma- 

 nent." Many other quotations of the same 

 kind may be made. As a matter of fact six 

 years elapsed, during which active investi- 

 gation in this department was being prose- 



* Lecture before the Royal Institution of Great 

 Britain. 



