S56 Dr. R. Hare on Improvements in the 



The plate in the centre of the stream shows less rusting 

 than the one at the edge in still water ; but judging from the 

 analogous case of the copper sheathing of a ship, it should 

 waste away the fastest, the particles of peroxide of iron as 

 they are formed being removed by the force of the stream, 

 while the voltaic current developed during this action only 

 circulates to some other point of the same plate, or belongs 

 to what is called local action. 



From the above results, the benefit to be obtained in a con- 

 stant battery by making the negative plate rotate, should be 

 apparent ; but to prevent waste it would still be necessary to 

 employ one of the more costly metals, which are not liable to 

 oxidation. 



In concluding these experiments, I may again notice, that 

 a tube of oxygen suspended over a plate of iron in still water 

 has the same effect as the current of the stream, converting 

 the oxygenated plate into a platinode. The carbonic acid 

 present in all surface water may by some be thought to per- 

 form an essential part in the ordinary rusting of iron. But 

 where every care is taken to exclude this gas from a tube 

 filled with oxygen, a small quantity of water, and a piece of 

 iron, the oxidation of the iron proceeds with rapidity, accom- 

 panied by changes which appear to me to preclude the idea 

 that even a trace of carbonic acid can be essential. The oxy- 

 gen gas disappears ; at first an abundant formation of red or 

 peroxide of iron is seen ; then, after the supply of oxygen has 

 decreased, the green-coloured protoxide is gradually formed. 

 These two oxides afterwards begin slowly to unite, and form 

 the well-known black or magnetic oxide. In an experiment of 

 this kind every trace of the red and green-coloured oxides had 

 disappeared at the end of three months from the time of 

 closing the tube, and there remained only an inky precipitate, 

 which was proved to be the black oxide of iron. 



LVIII. On certain Improvements in the Construction and Sup- 

 ply of the Hydro-Oxygen Blowpipe^ by 'mhich Platinum 

 may he fused in the large txay. By Robert Hare, M.D.* 



/^N my return from Europe in 1836, I was very much in 

 ^^ want of a piece of platinum of a certain weight, while 

 many more scraps than were adequate to form such a piece 

 were in my possession. This induced new efforts to extend 

 the power of my blowpipe; and after many experiments, I 

 succeeded so as to fuse twenty-eight ounces of platinum into 

 one mass. 



* Conr,jnunicated by the Author. 



