THE EBBING TIDE. 461 



Alumina. The clay thus acted upon may, at 

 some subsequent period, become a source for 

 obtaining alum; and out of clays so formed, 

 alum is now obtained in large quantities on the 

 continent. 



The ebbing of the tide produces also im- 

 portant results to the animated and inanimate 

 dwellers on the sea-coast. Although this sub- 

 ject lies in obscurity, can we doubt that it is far 

 from being a matter of no moment to these 

 creatures that half their lives are to be spent 

 under water, and the remainder in the air? 

 Some may require more of the solar rays, or 

 more of the atmospheric oxygen than could be 

 obtained by total submergence. Or it may be 

 they require to separate and discharge gases into 

 the air in exchange for others which they re- 

 ceive, and that these processes could not be 

 accomplished in the water or in the air alone. 

 However this may be, it is highly probable 

 that the all-wise Creator, in appointing as He 

 has done a zone of exposure to atmospheric 

 and solar influence to some of these marine 

 inhabitants, which has been denied to others 

 which cannot live under similar circumstances, 

 has at the same time appointed it with a view 

 to the fulfilment of certain functions of which we 

 remain at present almost entirely ignorant. 



The return of the tide is the signal to all 



