26 JOURNAL OF THE 



NOTES ON THE DEFLECTIVE EFFECT OF THE 

 EARTH^S ROTATION AS SHOWN IN STREAMS. 



BY COLLIER COBB. 



So early as 1837, Poisson produced his general equations 

 for determining the influence of the earth's attraction and 

 rotation on the apparent motion of a projectile, and he 

 applied them to the case of a material point constrained to 

 move on a given curve and attached to the surface of the 

 earth, omitting the effects of friction and the resistance of 

 the air. 



In 1859, Ferrel published in Riinkle^ s Mathematical 

 MontJily his celebrated paper on the Motions of Fluids and 

 Solids on the Earth'' s Surface^ in which he stated that, "In 

 whatsoever direction a body moves on the surface of the 

 earth, there is a force arising from the earth's rotation 

 which deflects it to the right in the northern hemisphere, 

 but to the left in the southern." 



Karl E. von Baer, in a paper, Ueber ein allgenieines 

 Gesets in der Gestaltitng der Flussbetten^ published in the 

 bulletin of the Imperial Academy of Sciences of St. Peters- 

 burg, in i860, showed that the observed changes of posi- 

 tion in streams might be explained as a consequence of the 

 earth's rotation ; yet the makers of our scientific text- 

 books have not taken the pains to give a correct, or rather, 

 a complete, statement of the true value of this deflective 

 force. Dana states it clearly and correctly in his Manual 

 of Geology;* but Geikief speaks of it as an easterly^ a 

 westerly deflection, seeming to regard it as a getting left 

 behind, and the same expression is used by ReclusJ in 

 speaking of the rivers of Gers. 



Von Baer's explanation does not account for the fact that 



Third edition, p. 650. fThird edition, 1S93, pp. 15, 16. % La France, pp. 115, 116. 



