340 ON A DIRECT METHOD OF OBTAINING IODINE. 
of Woods and Forests for permission to cut the seaweed from 
the rocks, the preliminary object being to make compara- 
tive experiments on the particular period of growth at 
which these marine productions contain the largest amount 
of the element in question. Various circumstances, how- 
ever, partly local, partly arising out of the nature 
of the case, rendered this formality unnecessary ; it 
was, in fact, soon determined, that, in the earlier periods of 
growth, iodine is almost absent, progressing however with 
the advance of the plant, and at the maximum, at the precise 
period when the weed yields to the autumn tempests and 
is drifted on the .shore, thus saving all the additional ex- 
pense and risk of collecting from the rocks. Assuming then 
that two main points are established, viz. that the most fer- 
tile source of iodine is in the laminarian species, and in them 
at the period when their perennial functions are completed, 
we may allude to the present mode of obtaining the ele- 
ment from the ashes of the plant, which we shall designate 
the kelp process, and show how the assumed facts influence 
the operations of the manufacturer, or rather the impossi- 
bility of obtainingthe maximum advantage derivable from a 
proper application of these facts, with the present mode of 
extracting iodine by the kelp process. All sea-weed con- 
tains a very large proportion of sea-water; in the small 
shallow-water species this can be removed, by exposure in 
summer to the wind and sun, without great difficulty ; in 
the other species, on the contrary, even under the most fa- 
vorable circumstances, decomposition will occur before 
the plant can be brought into a condition favorable for its 
combustion ; the consequence is, that the kelp process is 
principally confined to a species which contains but a small 
portion of iodine, and to a period of the year at which the 
other species has not arrived at maturity. The disadvan- 
tage does not rest here. The temperature, in forming kelp 
cannot be so nicely controlled as to prevent the more vola. 
tile iodides being dissipated, or, what is of still more fre- 
