286 Distribution of Iodine. 



temperature. The action of alkalies particularly explains 

 why all alkaline mineral waters are iodurated. 



It is superfluous to remark that subjacent rocks, or such 

 as are mixed with the arable soil in the midst of which their 

 decomppsition is going on, necessarily add more or less 

 iodine in proportion to the quantity of it they themselves 

 contain. Thus the millstone rock, in which iodine abounds, 

 — the coarse limestone, where it is in a smaller proportion, — 

 the plastic clay, where it is accumulated, — the middle and 

 upper oolites, which often contain considerable quantities, — 

 talc rocks, and clay-slates, where it is rare, — the limestones 

 and saccharoidal dolomites, in which it does not exist, — evi- 

 dently cannot yield an equal quantity to the soil. 



In recapitulation, three circumstances, namely, its own na- 

 ture, the subjacent rocks, and the quality and quantity of the 

 rain-water, influence the richness of arable soil in iodurets. 



Alimentary matters are differently iodurated, according to 

 the soil which produces them. I have found less iodine in 

 the maize of Aosta and Aiguebelle than in that of the plain 

 of Alexandria ; in the wanes of Saint-Julien-en-Maurienne, 

 and of Moutiers, than in those of Montmelian and of Asti, 

 and especially in the wines of Burgundy, Orleans, and Bour- 

 deaux ; in the forage of the valleys of Arc, of Isere and of 

 Doire-Baltee, than in those of the valleys of the Seine and 

 the Loire ; in the milk and cheese of Mont-Cenis, and of the 

 farm of Cassines-Saint-Martin (near Aoste), than in the same 

 products bought in the Paris market ; in the corn of the right 

 bank of the Valley of Graisivaudan, than in those of the oppo- 

 site bank. 



We now clearly perceive, why the atmosphere of the valleys 

 of the Alps, which is little influenced by the general currents 

 of the air, have not, moreover, an appreciable and pecu- 

 liar ioduration. It is because the soil, yielding only very 

 minute traces of iodurets in the waters which wash it, which 

 w^aters, having fallen from an atmosphere nearly deprived of 

 iodine, have in their turn almost none to bestow upon the soil. 



B. There is a general coincidence between the amount 

 of iodine in the air, the waters, the soil or alimentary pro- 



