No. 144.] 259 



Those matters which go into the sea, however, are not irrevo- 

 cably lost. Those who were present at this club two years ago, 

 when Prof. Mapes explained some of the means by which these 

 are returned, will need but a few remarks to recall that explana- 

 tion, and with your indulgence I will briefly state some of the 

 more important points. 



All soluble or movable constituents of the earth's surface are 

 liable to displacement by the action of rains, wastages, &c., and 

 may be carried to the ocean by means of rivers. So great is this 

 apparent waste that it is said that a sufficient quantity of fertiliz- 

 ing matter passes the city of New-Orleans in twenty-four hours 

 to fertilize a county. In the economy of nature this is restored 

 to the requirements of vegetation in many and diiferent ways. 



Marine plants contain large quantities of inorganic matter, and 

 these are often used as a manure, while the employment of their 

 ashes in the manufacture of kelp, soda, and iodine is a means of 

 their being restored to the soil. 



Many fish, such as shad, herring, mackerel, &c., live near the 

 mouths of large rivers, where the foreign matter is so largely pre- 

 sent as to afford them support, and they yearly migrate to the 

 upper parts of the river, where they find water sufficiently pure 

 for the development of their ova. These fish are caught in large 

 numbers, and thus reach the soil, while their ova are eaten by 

 amphibious animals, and through their assistance become valu- 

 able to man. All fish caught and used as food return to the soil 

 matters which had been carried to the sea in the water of rivers. 



Shells are another source of return ; so are birds that live on 

 fish, such as birds that frequent the guano islands. Sea foam and 

 spray are sometimes carried by the winds to a distance of sixty 

 miles from the shore, and at this distance leaves have been found 

 with salt on them, it having been carried there in spray and crys- 

 talized on the evaporation of the water. 



The evaporation of sea water may be another means of return. 

 Cold sea-water may absorb twice its bulk of chlorine, and when 



