KELP. 485 



from it in the form of smoke, while the earthy 

 and saline remain behind in the fused bluish 

 mass called kelp. Twenty-four tons of sea- 

 weed, at a medium, yield one ton of kelp. Kelp 

 contains chloride of podium, carbonate of soda 

 a product of the combustive process, chloride 

 of potassium, and traces of the other mineral 

 constituents of sea-water. In addition to this, 

 kelp, after undergoing chemical treatment, is 

 found to contain sensible proportions of the re- 

 markable element iodine, and very minute traces 

 of another element, bromine. 



The existence of these various elements in 

 the ashes of marine plants leads us to ask by 

 what means they were obtained? The roots 

 of sea-weeds differ from those of terrestrial 

 plants both in their structure and offices. 

 They are not the channels of nutriment be- 

 tween the soil and the plant. They appear 

 simply intended to anchor the plant, to enable 

 it to resist the violence of the waves. They 

 most commonly embrace a rock or a stone, 

 from the compact and obdurate surface of which 

 no soluble matter for the nutrition of the plant 

 can be extracted. Many float, unattached, hun- 

 dreds of miles from any shore, and in deep water. 

 It is plain, therefore, that the whole sum of 

 the ingredients forming a sea-plant is obtained 

 from the water in which it floats. A reference 



