SUPPLY OF OXYGEN. 145 



the bountiful Author of every perfect gift opens 

 His hand, and they are filled with good. Man is 

 not the principal beneficiary for whom provision 

 is made in the qualities of marine plants; the 

 humblest of his fellow- creatures share with him 

 the ample supply which divine beneficence has 

 prepared. 



But another important truth demands our ad- 

 miration of the divine wisdom and care by which 

 the processes of physical nature are carried on. 

 It is now fully understood that on the land the 

 great source of oxygen requisite to animal life is 

 the vegetable kingdom ; that a continued recipro- 

 cation of benefits, so to speak, takes place between 

 animals and plants, the latter consuming the 

 carbon produced by the former, and the former 

 living on the oxygen exhaled by the latter. 



The same process is carried on beneath the 

 waters. The marine animals which live upon 

 sea plants also require oxygen, without which 

 their vital functions cannot proceed. This oxygen 

 their organs of respiration separate from the 

 liquid element in which they live. But the sea- 

 water would thus soon cease to be capable of sup- 

 porting its countless hosts, if some provision were 

 not made for the renewal of the life-sustaining 

 fluid strained from it by the respiration of 

 animals. This renewal, however, is effected by 

 aquatic plants. They are, like land plants, the 

 great source of oxygen ; they afford, therefore, 

 food and vital air to the denizens of the deep, 

 from whose decay they in return obtain carbon 

 L 



