548 PKOCEEDIXGS OF THE WASHINGTON MEETING 



SCIENTIFIC RELIEF MAPS 

 BY G. C. CURTIS 



The subject of the latter paper was discussed by C. W. Haj^es, W. M. 

 Davis, and the author. A short abstract is printed in Science, volume 

 xvii, page 222. 



The Society adjourned for the noon recess, following which Mr Norman 

 W. Carkhufif, in charge of the Photographic Laboratory of the Geological 

 Survey, gave a demonstration of the process and instrument for '' day- 

 light development '' of kodak films. 



The Society reconvened at 2.10 p m. 



The first paper of the afternoon session was the following : 



ORIGIN OF OCEAN BASINS ON THE PLANETESIMAL HYPOTHESIS 

 BY T. C. CHAMBERLIX 



[ A bstract] 



The planetesimal hypothesis of the origin of the solar system differs fundamentally 

 from the Laplacian and other gaseous hypotheses, and from the meteoroidal hy- 

 pothesis as set forth by Lockyer and Darwin. These latter assign the extension 

 of the parent nebula to the opposed movements, collisions, and rebounds of the 

 constituent molecules or meteoroids. The former assigns it to concurrent orbital 

 movement. In the gaseous and meteoroidal hvpotheses (as usually understood) 

 the aggregation is the simple work of gravity following a reduction of the oscilla- 

 tory and colliding action. In the planetesimal hypothesis the aggregation is de- 

 pendent on orbital conjunction. In the former the aggregation is massive and 

 relatively rapid; in the latter the aggregation is individual and relatively slow. 

 In the gaseous hypothesis the temperatures are necessarily very high, and the 

 planets are formed by detachments. In the meteoroidal conception of George 

 Darwin, the conditions are practically the same, and in that of Lockyer they differ 

 rather in degree and in detail than in essence. In the planetesimarconception 

 the planets grew up separately by innumerable accretions of infinitesimal plan- 

 etoids (planetesimals), and the external temperatures were not necessarily high, 

 since the orbits of the planetesimals were normally direct and concurrent and the 

 aggregation came about by overtakes in contradistinction to opposed collisions, 

 and the frequency of these was limited by the concurrent direction of orbital 

 movement. 



The paper outlined the hypothetical origin of the ocean basins under the plan- 

 etesimal theory, and set forth the simple self-selecting process by which they were 

 perpetuated and deepened, and the connection of this with the dynamics of defor- 

 mation. 



The paper was discussed by A. C. Lane, H. F. Reid, G. P. Merrill, 

 G. K. Gilbert, G. F. Becker, Bailey Willis, and the author. 



