OF ARTS AND SCIENCES: JANUARY 25, 1871. 307 



particles of the ocean waters from the shore will be followed by a 

 similarly small fluctuation of the level along the coast. 



The observations of the rise of the tide give us the result of the 

 effect of all the causes without the possibility of distinguishing the 

 power of each of them separately. In fact, the elevation of the level 

 corresponds to each periodical current from the ocean; thus, to explain 

 some inequalities of the heights of tides, we must consider the causes 

 from which the periodical currents may proceed. For instance, the 

 diurnal inequality of heights is observed in all morning and evening 

 tides, which undergoes a periodical change according to the season of 

 the year. But, on the other hand, the difference between the heating 

 of the waters by the sun along the shore (where the diurnal amplitudes 

 in the temperature are very considerable) and in the ocean will cause 

 the periodical currents. Certain other inequalities in the heights of 

 tides will also proceed from the periodical and accidental variations in 

 the direction and rate of the constant local currents. The power of 

 the wind to drive the waters into the bays increases the height of the 

 level. The anomalies in the phenomena of tides are explained by the 

 interferences of the currents, and by the streams caused by the differ- 

 ence of the level in the nearest points. 



Six hundred and twenty-eighth Meeting. 



January 25, 1871. — Stated Meeting. 



The President in the chair. 



There being no quorum for the transaction of business, the 

 matters which should have been acted upon at this meeting- 

 were postponed. 



The President announced the death of Professor William 

 Chauvenet, Associate Fellow of the Academy. 



Professor N. S. Shaler made a communication on the Geol- 

 ogy of the region about Richmond, Ya. He claimed that the 

 sienite ridge which occurs at that point was of later elevation 

 than the rest of the Appalachian Ridge, which it clearly resem- 

 bled in many important regards ; furthermore, that the salient 

 angle of Cape Hatteras was caused by the elevation of this 

 ridge. Mr. Shaler also claimed that the Cincinnati axis of 



