44 PECULIAR TRIBES OF ALGJE. RED SNOW. 



ing kindled a fire on the sand, supplied it with some dry sea- weed 

 as fuel ; and that under the ashes, a mass of vitrified matter was 

 afterwards found, resulting from the union at a high temperature, 

 of the soda of the sea- weed, with the silex of the sand. Many 

 Algae also constitute a very valuable manure; and might be 

 much more used than they are. But one of their greatest bene- 

 fits to Man, consists in the Iodine with which they supply him ; 

 a substance which is of the most important use to the Phy- 

 sician, in the treatment of many diseases, and which is a nearly 

 certain cure for some, which were formerly considered almost 

 irremediable. One species, moreover, which abounds on flie 

 shores of China, furnishes a glue and varnish to the Chinese, 

 even superior to that which is obtained from animal matter in 

 this country. It seems, when once dried, to resist the action of 

 water ; for it is employed to fill up the lozenge-shaped inter- 

 stices in the network of Bamboo, of which windows are fre- 

 quently constructed ; as well as to strengthen and varnish the 

 paper of their lanterns. A species abounding on the southern 

 and western coasts of Ireland furnishes a good size for house- 

 painters ; and there are many others, which contain an amount of 

 gelatinous matter, that might be rendered useful in various ways. 



47. Besides the tribes of whose character a sketch has been 

 thus given, there are others of a doubtful nature, which are 

 generally referred to this group ; although some peculiar charac- 

 ters which they exhibit, and their similarity to certain animal 

 forms, render it doubtful whether they ought not to rank with 

 that kingdom. They are mostly formed of cells jointed together, 

 as the Confervas ; but some of them seem to possess a different 

 interior structure ; and others exhibit very curious motions, which 

 can scarcely be distinguished with certainty from those of animals. 

 In one of these groups, a large quantity of flinty matter is con- 

 tained in the walls of the cells ; so that they perfectly retain their 

 form, after all the vegetable structure has been destroyed, by the 

 action of heat and acids. The cavity of the cells, too, is some- 

 times seen to be partly occupied by large angular crystals. All 

 the plants (if such they be) of this group are very minute. 



48. There is, however, a group yet simpler than these, of the 

 vegetable nature of which there is no doubt- On the damp parts 



