The General Distribution of Iodine, 187 



would represent the oldest vegetation of the globe. Fresh 

 water animals contain iodine ; they even contain more than 

 the plants which grow in the same water. From numerous 

 experiments, it may be presumed that iodine exists in varia- 

 ble proportions in all the waters of the globe. The richness 

 of waters in iodine may be presumed according to the more 

 or less ferruginous nature of the lands they wash. The pro- 

 portion of iodine ordinarily increases in water with that of 

 iron, so that waters which are called ferruginous, might just 

 as properly be called ioduretted waters. Waters of igneous 

 rocks are more ioduretted on the average, and especially 

 more uniformly than those of sedimentary earths. The 

 waters of the coal formation are rich in iodine, but the waters 

 of essentially calcareous and magnesian earths contain very 

 little of this substance. Iodides are not necessarily propor- 

 tional to the chlorides. Waters of rivers are, on an average, 

 more ioduretted and less charged with earthy salts than 

 those of springs ; the waters of wells, however, are at once 

 most calco-magnesian and least ioduretted. The proportion 

 which exists between the iron and the iodine of waters, the 

 easy decomposition of the iodide of iron, and the complete 

 decomposition of the iodide of the waters in evaporation 

 without the addition of potassa, render it probable that the 

 iodine exists in them as iodide of iron. Fermented liquors 

 contain iodine : wine, cider, and perry, are more ioduretted 

 than the average of fresh waters. Milk is richer in iodine 

 than wine ; independently of the soil, with which it varies, 

 the proportion of iodine in milk is in the inverse ratio of the 

 abundance of that secretion. Eggs (not the shell) contain 

 much iodine. A fowl's eg^ weighing fifty grains, contains 

 more iodine than a quart of cow's milk. Iodine exists in 

 various soils. It is abundant in sulphur, and in ores of iron 

 and manganese, and sulphuret of mercury ; but rare in gyp- 

 sum, carbonates of time, and silicious earths. Any attempt 

 to extract iodine economically, should be made from fuci. 

 Most of the bodies regarded by therapeutists as pectoral and 

 anti-scrofulous are rich in iodine. 



Iodine in Aluminous Slates. 

 Some years ago M. Forchammer brought forward an inge- 



