Partial Fusion of Metal by the Electric Discharge. 73 

 trate of iron, and dissolving this precipitate (sweetened, and 

 freed from the greater part of the water), by little and little, 

 with sulphuric acid, which ought to be concentrated, in 

 order to obtain, without evaporation, crystals of sulphate of 

 hyper-oxya:enated iron. This salt possesses an incompara- 

 ble astringency. 



The operation of the transmission of oxygen appears to 

 manifest itself the more upon pieces of linen simply dipped 

 in acetate of iron, and maddercd, since we are obliged, in 

 order to bleach them completely, to expose them a long time 

 in the field, if we do not choose to make use of the artificial 

 process of bleaching. The printed parts of these pieces of 

 cloth are often weakened, and appear sometimes as if pierced 

 with a sharp instrument, or burned with a concentrated acid: 

 such a circumstance could not occur, except from the action 

 of the oxygen of the coloured oxide of iron, oxygen being 

 successively restored to this oxidable body by the atmospheric 



air. 



Minerals do not present the only substances which ox- 

 idate gradually, and by intermediate terms. 



Indigo furnishes a proof that vegetables (and I may add 

 also that animals) will produce similar results ; for a so- 

 lution of any kind of indigo (I except, however, the sulphate 

 of indigo) may, in de-oxidating or in recovering oxygen, 

 pass through all the degrees of the shades of blueish green, 

 even to that of a very yellow olive, and yet preserve the 

 same quantity of indigo in solution. The beauty and soli- 

 dity of the bfues for dyeing, and of the blue for pencilling, 

 depend nuich on the dlflerent degrees of oxidation. 



XIV. On the partial Fusion of Metals by the Electric 

 Discharge. By a Co-respondent. 



To Mr. Tilloch, 



SIR, 



I TAKE the liberty of sending you some further experiments 

 and observations on the partial fusion of thin plates of me- 

 tal, &.C. an account of which you was so kind as to msert lu 



your 



