SPONGES. 277 



its natural state, this sponge contains about one 

 per cent. It might, therefore, be a profitable 

 speculation to extract this useful element from 

 such sponges as S. oculata that abound on some 

 of our English coasts. It is probable, also, that 

 if all the different varieties of sponges, polypes, 

 star-fish, etc., which are left to putrefy upon our 

 shores, were properly collected, they would prove a 

 valuable source of iodine and bromine, which are 

 now, in spite of their high price, so much used in 

 the chemical laboratory and by photographers. In 

 places where sponges are abundant, the commoner 

 sorts would prove useful to manure manufacturers, 

 on account of the large per-centage of nitrogen 

 they contain. They are soluble in strong acids, 

 and also in alkaline solutions. It has been found 

 the 8. tomentosa (S. wrens], which is common upon 

 the coasts of England and North America, will 

 raise blisters when rubbed upon the hand ; and if 

 previously dried in an oven, its stinging faculty is 

 much increased. 



According to Dr. J. S. Bowerbank, the flints of 

 the chalk formation, and the beautiful moss agates 

 which every one admires, are of spongeous origin ; 

 that is to say, have been formed by sponges which 

 are now fossil. In fact, agates and flints are, 

 according to this author, petrified sponges. It is 

 indeed true that the polished section of a moss 



