416 J. LeConte — Apparent Attractions and Repulsions 



In conclusion, it may be said that the country covered with 

 "Artemesia Gravel" gives no evidence of any morainic origin 

 of the deposits, but rising from the great subsidence of the 

 Terrace Epoch, it was first an exposed island, and afterward it 

 formed a more extended margin, as the waters were contracting 

 to within their present basins. 



When the ancient beaches and terraces in the whole region of 

 the Great Lakes shall have been carefully measured and studied 

 with reference to their original extension, then there may be 

 some accurate data for the determination of the relative amounts 

 of local and general oscillations of the continent, for we see 

 that the above fragmentary lists of elevations show a close 

 relation between the different beaches, which would doubtless 

 be further borne out, were the measurements more complete, 

 and made with a view of arriving at true sci entitle results. 



Although the apparent attractions and repulsions of small 

 floating bodies is one of the most, familiar phenomena, and one 

 of the earliest to which the physical theory of capillarity was 

 applied, yet it remains a perplexing puzzle to a large i 

 of intelligent students. This 

 popular explanations given in 

 mentary physics do not bear a critical examination and are. 

 consequently, anything but satisfactory to the student who 

 endeavors to secure a clear physical conception of the cause of 

 these motions. 



This class of phenomena seems to have been first explained 

 by the celebrated Mariotte about 1655; but more particularly 

 by the great geometer Monge,* who distinctly and correctly 

 referred them to the action of the surface film of the liquid, as 

 modified by the presence of the partially immersed solid 

 bodies. In more modern times, the improved theory of capil- 

 lary action of Youngf and Lapiace,t as modified by the refined 

 physico-mathemafieal investigations of Gauss. .^ and of Pois- 

 son,| refers all capillary phenomena not only to the reciprocal 

 between the liquid and the solid, but also to the 

 f a tense superficial film at the free surface of every 



S ill' 1 A'-jul. de Scicm-i-S Inf I 7 s 7 . |». .".Illi ft. >o.|. 



soc.) — Also. ■■Siqij.lrmri!! ,'i !;,, Theorie ile [/Action I'upillinn'. 

 .' ; tilil.rii.'' (li,t - 



