METAMORPHOSED FUCOID SCHISTS IN SCANDINAVIA. 159 



It appears from these analyses, that the fueoidal plants principally separate 

 sulphuric acid from the sea-water ; the quantity of it is always very large, and 

 never less than 1*28 per cent, of the weight of the whole dried plant. In one 

 plant it amounted to 8'.50 per cent., a quantity which is quite enormous con- 

 sidering the vast masses of fueoidal plants which grow in the sea ; and I think 

 that on an average we may take four per cent, of sulphuric acid in the dry 

 sea-weed ; for the mean of nineteen analyses gave 3'82 per cent. This acid 

 is combined with potash, soda and lime, and would, after the decay of the 

 plant, again be dissolved in the water of the ocean, were it not for an action 

 which I shall afterwards describe. 



Next to sulphuric acid the potash is the most interesting of the constituent 

 parts of the ashes of Fucus. It occurs in a very small quantity in sea-water, 

 and certainly constitutes a great portion of the Fucus tribe, which on an ave- 

 rage contains two and a half per cent, of the dried plant, the mean quantity 

 found in fourteen analyses being 2'52 per cent. 



Next to the potash, the magnesia deserves the attention of the reader. On 

 an average there is about one per cent, of the weight of the dried plant pre- 

 sent in the ashes, a quantity which exceeds that of the lime, and may still 

 exceed it more than appears from the tabular view, because no inconsiderable 

 quantity of lime depends upon the numerous small shells and corals which 

 adhere to the sea-weeds. In fact it might be doubted, whether any lime at all, 

 in form of carbonate of lime, or such salts of lime whose acid by combustion 

 forms carbonates, exists in the plants of the Fucus tribe, and whether all the 

 lime belonging to the constitution of these plants is not combined with sul- 

 phuric or phosphoric acid. Magnesia occurs in great quantities in sea-water ; 

 the animals of shells and corals seem to have no attraction whatever for this 

 substance, while the causes that bring it into the ocean are constantly acting, 

 and thus its quantity might go on increasing. The fueoidal plants, however, 

 absorb some portion of this vast quantity of magnesia and deposit it in the 

 beds, which contain the solid substances of the sea-weeds, as far as they are 

 insoluble in water. 



Phosphoric acid always occurs in the ashes of sea-weeds and is probably 

 always combined with lime. 



I must still mention chlorium among the substances that occur in the Fucus, 

 but its quantity is very variable, and there is no doubt that some of these 

 plants (at least at certain seasons) contain no chlorium ; and where only small 

 traces of this substance have been found, as in the jEcklonia buccinalis, Iridcea 

 edulis, and Delesseria sanguinea, they derive it from the salts of sea-water still 

 adhering to the dried plants. On the other hand, it is highly probable, that 

 the quantities of chlorium which are found in some instances are not acci- 

 dentally present, and that chlorium probably combined with sodium plays (at 

 certain seasons) a considerable part in the life of the fueoidal plants, while it 

 may disappear at others ; for potash occurs in considerable quantities in the 

 potatoe while it is flowering, but diminishes afterwards. 



A specimen of Fucus vesiculosus, taken in August 184'4< in the Sound, washed 

 and dried, left when heated in a close vessel 28"88 per cent, charcoal, which 

 again left 13"33 percent, ashes; the quantity of real charcoal thus being 

 15'55 per cent. 



This chemical constitution of the ashes of the Fucus tribe explains several 

 great phsenomena in the general life of nature. It is now very little doubted 

 that the original fertility of the soil, and even partially that which has been 

 occasioned by manure, depend upon the mineral substances which play either 

 a permanent or a transitory part in the life of the plants, and among such, 

 sulphuric acid, phosphoric acid and potash, are those which, occurring in the 



