136 The General Distribution of Iodine. 



rivers entering the Mediterranean is inhabited both by fluvia- 

 tile and marine species. 



In 1817 M. Beudant published a paper on the Phenomena 

 of Crystallization, treating especially of the variety of forms 

 assumed by the same mineral substances. He was also the 

 author, in 1837, of two treatises on Mineralogy and Geology, 

 which are much esteemed ; that on Geology having passed 

 through five editions, and being adopted by the University of 

 France as a text-book. — Journal of the Geological Society, 

 No. xxvi., p. 25. 



The General Distribution of Iodine. 



The existence of iodine in marine and fresh-water aquatic 

 plants from all quarters of the globe, is evidence of the very 

 general distribution of this substance.* The state of the earth 

 at the periods of the old vegetation might be deduced from the 

 proportion of iodine in their fossil remains. Coal, which is 

 rich in iodine, must arise from plants developed on lands still 

 washed by the sea ; in anthracite, which contains less iodine 

 than bituminous coal, we find that terrestrial vegetables have 

 become mixed with cryptogamic plants of the coal formation ; 

 and the lignites, which contain little iodine, shew that the 

 terrestrial species then predominated over the crust of the 

 globe. Iodine appears in the lixivium of peat; and its 

 abundance in graphite seems finally to shew, that this sub- 

 stance should be classed among products of organic and 

 aqueous origin. Anterior to the coal formation, graphite 



* Mr Chatin concludes from his experiments ; — 



(1.) That those plants growing in running waters, or on the borders of large 

 bodies of water which may be strongly agitated by the winds, contain more 

 iodine than those of stagnant waters. 



(2.) That the proportion is very small in species that are imperfectly sub- 

 merged or only at intervals. 



(3.) That the proportion of iodine appears to be independent of the nature 

 of the plant or its place in the natural system. 



The antiscrofulous effects of the cress, Veronica Phellandrium, &c., are 

 explained by the presence of iodine. 



Professor Balfour says, — " The larger quantity of iodine contained in plants 

 growing in running water, may depend on the constant renewal of iron in solu- 

 tion, — ^tbe Wftter containing salts of iron." 



