ON A DIRECT METHOD OF OBTAINING IODINE. 339 
marine productions to act as her storehouses for the accu- 
mulation of certain inorganic bodies^essential to terrestrial 
vegetation, and which, but for this provident care, would 
rapidly be out of human reach, In the Isle of Man this 
economical arrangement is peculiarly necessary. The more 
soluble portions of the granite, felspar, clay-schist, &c, 
which by attrition and solution are rapidly conveyed to the 
sea, are thus again presented to the agriculturist, and that 
in a condition admirably adapted for assimilation by the 
organs of plants ; without this wise provision, he would be 
principally dependent for alkaline salts on masses of hard 
intractable rocks, the mechanical state of which would na- 
turally form an almost insuperable barrier to the process of 
absorption. Referring to the excellent work of the Rev. 
J. G. Cumming for information on the geology and locali- 
ties of the island, we now proceed to the principal chemical 
features of the two classes of sea- weed to which we have 
alluded; and it may be stated, as the general result of ana- 
lysis, that the metallic base preponderating in the Fuci is 
sodium,* combined with oxysulphion, chlorine, and small 
quantities of iodine and bromine ; whilst the plants which 
flourish in what Prof. E. Forbes has denominated the lami- 
narian region are characterized by containing a preponder- 
ating quantity of potassium, with a far larger proportion of 
iodine than in the former species, and are on this account 
therefore of more interest and importance to the manufac- 
turer. Many practical difficulties however prevent the 
maximum advantage to be derived from the above facts in a 
manufacturing point of view ; and, in order to obviate them 
as much as possible, the writer was induced, at the com- 
mencement of his research, to apply to the Commissioners 
*Prof. Thompson states, on the authority of Gaultier de Claubry, 
that the Fucus serratus contains more iodine than F. digitatus or 
vesiculosus. The experience of the author is directly the reverse, 
presuming that the F. digitatus is identical with what is now denomi- 
nated Laminaria digitata. 
