166 On the Elevation of Beaches by Tides. 



the same substances that had been introduced into the flask, and 

 also after having subjected them to a boiling temperature. In 

 order now to renew constantly the air within the flask, I sucked 

 with my mouth, several times a-day, the open end of the appa- 

 ratus filled with solution of potash ; by which process the air 

 entered my mouth from the flask through the caustic liquid, and 

 the atmospheric air from without entered the flask through the 

 sulphuric acid. The air was of course not at all altered in its 

 composition by passing through the sulphuric acid in the flask, 

 but if sufficient time was allowed for the passage, all the portions 

 of living matter, or of matter capable of becoming animated, 

 were taken up by the sulphuric acid and destroyed. From the 

 28th May till the beginning of August, I continued uninter- 

 ruptedly the renewal of the air in the flask, without being able, 

 by the aid of the microscope, to perceive any living animal or 

 vegetable substance, although during the whole of the time I 

 made my observations almost daily on the edge of the liquid ; and 

 when at last I separated the diff^erent parts of the apparatus, I 

 could not find in the whole liquid the slightest trace of infusoria, 

 of conferva?, or of mould. But all three presented themselves 

 in great abundance a few days after I had left the flask stand- 

 ing open. The vessel which I placed near the apparatus con- 

 tained on the following day vibriones and monades, to which 

 were soon added larger polygastric infusoria, and afterwards 

 rotatorige. 



1. On the Elevation of Beaches by Tides. 2. On Ripple-Marl:. 

 uyS^^ 1. Elevation of Beaches by Tides. 



If the earth were a spheroid of revolution, covered by one 

 uniform ocean, two great tidal waves would follow each other 

 round the globe at a distance of twelve hours. 



Suppose several high narrow stripes of land were now to en- 

 circle the globe, passing through the opposite poles, and dividing 

 the earth''s surface into several great unequal oceans, a separate 

 tide would be raised in each. When the tidal wave had reached 

 the farthest shore of one of them, conceive the causes that pro- 



ce it to cease : then the wave thus raised would recede to the 



