68 INTRODUCTION. 



our British Alga, Gracllana coDiprcssa, and was probably 

 Gracilaria lichenoides, though several species and perhaps 

 genera answer the same purpose, as is the case with our 

 native mucilnginous Algse. Some say that Gigartina tenax 

 is the kind used by the Chinese for glue and fancy lanterns. 

 I learn from Glasgow that Agar- Agar began to be imported 

 about two years ago, under the belief that it would prove 

 highly serviceable in many respects. The main object in 

 view, however, was to employ it as a substitute for sago 

 flour, which is used by manufacturers to starch and stiffen 

 webs, and for this, on account of its gelatinous qualities, it 

 seemed admirably fitted. It has not yet been sufficiently 

 tried. The difliculty of completely dissolving it, has hitherto 

 been the obstacle to its extensive use. Were this overcome, 

 it would be of great service. As it is not costly, it may 

 come into repute as an agreeable article of food. AVe have 

 already mentioned that the blanc-mange wjiich is formed 

 from it, is exceedingly palatable, and, being the same in sub- 

 stance, must have all the nutritious vii'tues of the celebrated 

 Swallow-Nests so much prized by the Chinese. 



Even in our own most common Sea-wrack there are sub- 

 stances which may yet be turned to good account. One of 

 these is Mannife, the characteristic principle oi Manna, which 



