312 The Comijzercial Products of the Sea. 



again the form of ammonia. Thus we observe that in the 

 ocean a circulation takes place without the addition or 

 subtraction of any element, unlimited in duration although 

 limited in extent, inasmuch as, in a confined space, the 

 nourishment of plants exists in a limited quantity." 



We well know that the marine plants cannot derive 

 a supply of humus for nourishment through their roots. 

 Look at the great sea-tangle, the Fiiais giganteiLS. This 

 plant, according to Cook, reaches a height of 360 feet, and 

 a single specimen, with its immense ramifications, nourishes 

 thousands of marine animals ; yet its root is a small body, 

 no larger than the fist. What nourishment can this draw 

 from a naked rock, upon the surface of which there is no 

 perceptible change 1 It is quite obvious that these plants 

 require only a hold — a fastening, to prevent a change of 

 place — as a counterpoise to their specific gravity, which is 

 less than that of the medium in which they float. That 

 medium provides the necessary nourishment, and presents 

 it to the surface of every part of the plant. Sea water con- 

 tains not only carbonic acid and ammonia, but the alkaline 

 and earthy phosphates and carbonates required by these 

 plants for their growth, and which we always find as con- 

 stant constituents of their ashes. 



Seaweeds or fuci are used directly as manure, for the 

 manufacture of soda, iodine, bromine, and some like Irish 

 moss, etc., for the manufacture of gelose. Dried and 

 pressed seaweeds are also used for ornamental ,or botanical 

 purposes. In Scotland and other northern countries sea- 

 weed is used in winter for feeding horses, cattle, and sheep, 

 and is eaten by deer when other food is scarce. 



The beneficial effects in scrofulous swellings and goitre 

 of the vegetable ethrops and of the sponge charcoal, 

 which had been introduced by Armand de Villeneuve near 



