SCIENCE 



Editoeial Committek : S. Newcomb, Mathematics ; R. S. Woodward, Mechanics ; E. C. Piokbeing 



Astronomy; T C. Mendenhall, Physics; E. H. Thurston, Engineering; Ira Eemsbn, Chemistry; 



J. Le Conte, Geology; W. M. Davis, Physiography; 0. C. Marsh, Paleontology; W. K. Brooks, 



C. H-art Merriam, Zoology; S. H. Scudder, Entomology; C. E. Bessey, N. L. Bbitton, 



Botany; Henry F. Osborn, General Biology; C. S. Minot, Embryology, Histology; 



H. P. BowDiTCH, Physiology ; J. S. Billings, Hygiene ; J. McKeen Cattell, 



Psychology; Daniel G. Erinton, J. W. Powell, Anthropology. 



Friday, March 17, 1899. 



CONTENTS r 



The Oijective Presentation of Harmonic Sloiion (with 

 Plate II.) : Professor Carl Barus 385 



The Work of the U. S. Fish Commission 406 



Engineering and the Professions in Education : PRO- 

 FESSOR R. H.Thurston 407 



Scientific Books : — 



Loew's Die Chemischen Energie der lebenden Zel- 

 len : Dr. ALBERT F. Woods. Davis's Physical 

 Geographi/ : Professor Albert Perry Brig- 

 ham. General. Books Received 409 



Societies and Academies : — 



The Geological Club of the University of Minne- 

 sota : Dr. F. W. Sardeson. T/te Botanical 

 Club of tlie University of Chicago. Entomological 

 Society of Washington : Dr. L. O. Howard. 

 Tlie Academy of Science of St. Louis : Professor 

 William Teelease 412 



Discussion and Correspondence : — 



The Importance of Establishing Specific Place- 

 Modes : Professor Chas. B. Davenport. 

 Identity of Common and Labrador White-Fish: 

 Dr. Taeleton H. Bean. A Date-Pahn 

 Scale Insect : Professor T. D. A. Cockerell. 

 The Choice of Elements: T. D 415 



Astronomical Notes : — 



Tattle's Comet ; A New Star in Sagittarius : 

 Professor E. C. Pickering 417 



Notes on Pliysics : — 



Electric Wire Waves ; A New Indicator for Elec- 

 tric Waves ; Tlie Electric Discharge in Rarefied 

 Gas ; Brilliancy of Light Sources : W. S. F. Tlie 

 Magnetization of Iron ; General : A. St. C. D. ... 418 



Scientific Notes and News 420 



University and Educational News 424 



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

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

 sor J. McKeen Cattell. Garrlaon-on-Hudson N. Y. 



TEE OBJECTIVE PRESENTATION OF HAR- 

 MONIC MOTION. 

 CONTENTS. 

 Description of a Wave Machine. 



1. Introductory. 



2. General construction. 



3. Cam axles. 



4. Levers, riders and balls. 

 Action of the machine. 



5. Method of compounding. 



6. Plane transverse waves. 



7. Transverse space waves. 



8. Compressional space waves. 



9. Rotary polarization. 



ESPERIMENIS. 



10. Method of designating phases. Plane wavesi 



11. Do. Space waves. 



12. Effective cirles of reference. 



I. Compound S. H. M's coplanar of the same wave- 



length. 



13. Plane polarization curves. 



14. Waves of constant amplitude. 



15. Waves of varying amplitude. 



II. Preceding case (I) with additional velocity 

 superimposed on either wave-plane. 



16. Beats. 



17. Diippler's principle. 



III. Preceding cases (I and II) with the velocity 

 of either wave-train reversed. 



18. Equal velocities. Stationary waves. Reflec- 

 tion. 



19. Wandering nodes. 



IV. Component S. H. M's at right angles to each 

 other, of the same amplitude and wave-length. 



20. Elliptic polarization. 



V. Preceding case ( IV ) with component velocities 



and periods unequal. 



21. Incommensurable periods. 



VI. Preceding case (IV) with either component 

 velocity reversed. 



