316 The Commercial Products of the Sea. 



gardens ; and the bunches of vesicular grains which sup- 

 port these plants at the surface of the water, they name 

 tropical grapes. Up to the present time these seaweeds 

 have remained unutilized, doubtless because of the cost of 

 transport. 



Some of the species of seaweed are richer in ash than 

 others. The most generally diffused species, the Fucus 

 vesiculosus, or bladder-wrack, seems to withdraw the largest 

 amount of saline and earthy matters from the sea water. 

 Pereira, in analyzing the ash, found in it nearly 20 per cent. 

 of common salt, and u to 12 per cent, each of potash, 

 soda, and lime, and 24^ per cent, of sulphuric acid. 



FIG. 24. 



Varieties of Seaweed. 



Fresh weed usually yields 16 per cent, of ash, or 320 

 pounds to the ton of weed ; and each ton of ash would 

 yield 18 Ibs. of phosphates, iron and lime, 38 Ibs. of potash, 

 and other mineral substances, making up a total of 164 Ibs. 

 of valuable saline matter, or more than one-half of the 

 whole ash. 



Valuable as are many of these ingredients to plants, the 

 application of seaweed as a manure has some remarkable 

 properties which do not appear to be explained by analysis. 



