160 REPORT — 1844. 



least quantitj' in the soil, are notwithstanding absolutely necessary for the 

 growth of most of our cultivated plants. All these substances are constantly 

 washed out of the soil, and at last carried into the ocean, whose plants again 

 attract them ; and if the farmer that lives near the sea-shore transports the 

 sea-weeds as a manure for his fields, he thereby gives back to the land those 

 substances which rain has washed out of them. 



It is well known that innumerable small Crustacea, principally of the family 

 of the Amphipoda, live upon the Fuci of our shores, and hide themselves in 

 millions in the half-rotten heaps of those plants which the sea has thrown up. 

 They derive from this food phosphoric and sulphuric acid, lime and magnesia ; 

 and the ashes of the shell of the shrimp consist, according to my analysis, of 

 sulphate of lime, phosphate of lime, and phosphate of magnesia, with so little 

 carbonate of lime, that it seems merelj' to belong to small shells adhering to 

 the shrimps. It is well known that, directly or indirectly, the smaller Crustacea 

 constitute the principal food of fishes and cetaceous animals, and thus the 

 phosphate of lime in the bones of the larger marine animals is originally de- 

 rived from the sea- weeds ; and also in the ocean the phosphoric acid of in- 

 organic nature is, by means of plants, carried over to animals. 



The spontaneous decomposition of the fucoidal plants, and principally of 

 Fucus vesiculosus, is the following : after having during some days been ex- 

 posed to the action of heat and water, a fermentation begins, in which a great 

 quantity of carbonic acid is produced, and also a volatile substance which 

 seems not to differ from the common spirit of wine ; thus a complete vinous 

 fermentation takes place. When that has ceased, the whole mass begins to 

 rot, and a very complicated action commences, by whici: the sulphates are 

 changed into sulpliurets. M. Bischof of Bonn showed, many years ago, that 

 this effect takes place whenever the soluble sulphates come into contact with 

 organic substances exposed to putrid fermentation ; and whoever has observed 

 the masses of sea-weed left on the shore, will likewise have observed the smell 

 of sulphuretted hydrogen disengaged from the alkaline sulphurets by the 

 carbonic acid of the decomposing sea-weed and the atmospheric air. In the 

 neighbourhood of Copenhagen, the disengagement of sulphuretted hydrogen 

 from sea-weed is sometimes so strong, that the silver at the country places near 

 the shore is constantly blackened by the effect of that gas. 



If the sea-weeds in this state of decomposition come into contact with 

 oxide of iron, another change takes place, and the sulphur combines by 

 double decomposition with the iron and forms pyrites, while the oxygen com- 

 bines with the potassium, sodium and calcium. This decomposition is beau- 

 tifully shown on the western shore of the island of Bomholra in the Baltic, 

 where a ferruginous spring from the lower oolite flows into the sea in a small 

 beach, where a great quantity of Fucus vesiculosus is always thrown on shore. 

 All the rolled stones at the bottom of the sea are covered with a beautiful 

 yellow metallic coating of iron pyrites, which keeps unaltered so long as it is 

 covered by the sea, but which on being exposed to the air weathers to sul- 

 phate of iron. It is evident that this effect is produced in the present period, 

 since rolled pieces of bricks have even the same coating, where a ferruginous 

 spring which flows out of a borehole has hardly existed more than fifty years. 

 The same ettect takes place if a solution of sulphuret of potash is mixed with 

 ferruginous clay and left for some time in a close vessel ; the clay assumes a 

 black colour, and after it has been washed with water, diluted muriatic acid 

 disengages sulphuretted hydrogen and dissolves protoxide of iron. Thus it 

 follows, that wherever putrifying sea-weeds come in contact with ferruginous 

 clay, iron pyrites must be formed, which penetrates the clay, and on weather- 

 ing first forms sulphate of iron, and if no lime be present, will ultimately, by a 



