OF ARTS AND SCIENCES: JANUARY 9. 187-1. 803 



Berlin, acknowledging his election as Foreign Honorary 

 Member. 



The President announced the death of Professor E. J. 

 Cutler, Resident Fellow of the Academy. 



Professor J. D. Whitney continued the reading of his papei 

 on the remains of pre-historic man in California, left unfin- 

 ished at the last meeting. 



The following communication on the Tides, by Lieutenant 

 Roumiantzoff, was read. 



In the note "sur la theorie des marges" (Comptes Reyidus, May 16, 

 1870) I defined the phenomena of tidal vibrations. The view I take 

 on the subject is simply a development of the general idea expressed 

 by Laplace in his Mecanique Celeste. Laplace in fact established 

 that : — 



a. The phenomena of tides consist in the movements of fluid ; 



b. The infinitely small motion of particles of water is possible only 

 on the surface of their level ; 



c. The fluctuation of level on the coast is secondary in respect of 

 oceanic motion. 



At this time the physical description of the phenomena was very in- 

 sufficient, and the local circumstances on which the tides depended were 

 unknown ; consequently Laplace could not follow out the true prin- 

 ciples of his theory, and arrived in his final results at an assumption of 

 a certain proportionality between the phenomena of tides and the dis- 

 turbing forces. ( Vide Laplace, Mecanique Celeste, Tome V. Chapitre 

 XIII.) 



At the present time many of the peculiarities of the tides have been 

 s-hown by observers, and the principles which were wanting have been 

 mentioned in the remarkable works on "Tides" by the Astronomer- 

 Royal, Mr. Airy, Dr. Whewell, and others. These investigations have 

 caused the fundamental idea in Laplace's theory to be lost sight of; 

 so that until the present time the phenomena of tidal motion have been 

 examined as the disturbance of the form of waters in the ocean under 

 the influence of attracting bodies. At sea-stations we observe not the 

 form of the free surface of waters surrounding the solid globe, but the 

 result of the small horizontal vibrations of the particles of the ocean 

 waters ; and thus the investigation of the equations of the surfaces of 

 the ocean level does not include the theory of tides. Such an explana- 



