THE USES OF SEA-WEEDS. 63 



by tlie employment of manganese and sulphuric acid, which 

 react on each other and produce oxygen, which again com- 

 bines with hydrogen, and liberates the iodine, till now in 

 union with the hydrogen. The iodine escapes from the liquor 

 as a most beautiful violet-coloured vapour, which on cooling 

 condenses into a black, solid, crystalline body, in large glass 

 balloons arranged for the purpose. 



Iodine is extensively used as a medicine, combined with 

 potassium, with mercury, arsenic, &c. It is used also as a 

 tincture dissolved in alchol, and in combination with oils 

 if is much used as a liniment. Till some way of fixing it is 

 discovered, it is too evanescent to be used in dying or calico- 

 printing. In one respect the vapour of iodine is more 

 wonderful than the mysterious mist that we have all read 

 of, which, when liberated from the sealed box by the fisher- 

 man, consolidated and became a gigantic genie. Our violet 

 mist, which, like that of Arabia, has been dragged from the 

 sea, when artfully employed by man, can make the sun a 

 portrait-painter. The sun is a painter from the beginning ; 

 but the ingenuity of man, availing itself of iodine as an obe- 

 dient yet powerful genie, can make the sun a limner. My 

 young friends know that for the wonders of Calotype and Da- 

 guerreotype, the vapours of iodine are indispensably necessary. 



