27 



different metals to be ignited by the power of this battery, by joining 

 equal lengths of any two wires in the same line, and making the 

 circuit through both thus connected. In the comparison of platina 

 and iron, which of all metals are most easily ignited, the difference 

 was so little, that their comparative ignition altered during the ex- 

 periment in consequence of apparent difference in their capacities, as 

 well as conducting powers. Of other metals, gold and copper were 

 nearly equal, and far less easily ignited than the former. After them 

 stood zinc ; and last of all silver. Mr. Children observes, that the 

 order of these metals, as conductors of electricity, nearly follows that 

 of their powers to conduct heat. 



When this battery was excited to its utmost, it ignited 5 feet of 

 platina wire one ninth of an inch in diameter. 



A bar of platina, one sixth of an inch square and 2^ inches long, 

 was heated red, and fused at each end. 



A round rod, one fourth of an inch in diameter and 1\ inches long, 

 was heated bright red throughout. 



Oxide of tungsten was partially reduced. 



Oxide of tantalum was partly fused, and of a reddish brown colour. 



Oxides of uranium and titanium were fused, but not reduced. 



Oxide of molybdena was fused and reduced. 



Oxide of iridium, with osmium, was fused to a globule. 



Pure iridium was fused into an imperfect globule, having specific 

 gravity 18' 68. 



Of earthy bodies, ruby and sapphire were not fused. 



Blue spinel ran to a slag. 



Magnesia was agglutinated. 



Quartz was not affected. 



This opportunity was taken by Mr. Pepys of attempting the con- 

 version of iron into steel by union with diamond, which appeared to 

 have been accomplished. A wire of good soft iron, having been slit 

 longitudinally with a fine saw, the slit was filled with diamond powder, 

 and the whole having then been wrapped round with a piece of mus- 

 covy talc, was bound together with a fine iron wire. Although the 

 wire thus prepared was by no means intensely ignited, and for no 

 longer a time than six minutes, no part of the diamond powder was 

 to be found after the experiment, and the iron was found converted 

 into a sort of blistered steel ; for it was hardened by quenching while 

 hot, so as to resist the file, and to scratch glass with facility. 



Beside the experiments above made with three plates connected in 

 succession as a powerful battery by the action of acids on their sur- 

 faces, a trial was made whether at the moment of contact between 

 very large metallic surfaces, any degree of ignition could be rendered 

 visible. All the zinc plates were connected together as one zinc 

 plate, and also all the copper plates connected as one copper plate. 

 A communication was then made between the two sets of plates thus 

 connected, but not immersed in a fluid, and all the electricity sup- 

 posed to move in consequence of the contact, was made to pass 

 through a wire of platina iroWth of an inch in diameter, and about 





