64 Royal Society : — Mr. G. Gore on the Development of 



german-silver, when heated to redness, behaved like those of copper 

 in expanding regularly until a maximum was attained, and then con- 

 tracting slightly to a definite point whilst the battery remained con- 

 nected ; on stopping the current they contracted without irregularity. 

 When examined at lower temperatures, with a greater degree of 

 strain, no irregularity was observed. Various wires of aluminium 

 were examined ; the most suitable was one 0*88 millimetre thick, 

 20*4 centimetres long, with a strain of 12 ounces ; no irregularity 

 was observed at any temperature below redness ; aluminium expanded 

 and cooled very slowly, but less so than cadmium. Various wires and 

 ribbon of magnesium were also examined below a red heat, but no 

 irregularity of cohesion, except that due to gradual softening by heat, 

 was detected. 



All the metals examined exhibited gradual loss of cohesion at the 

 higher temperatures if a suitable strain was applied to develope it. It 

 is probable that if the fractions of time occupied by the needle in 

 passing over each division of the index were noted, and the wire 

 perfectly protected from currents of air, small irregularities of mo- 

 lecular or cohesive change might be detected by this method ; cad- 

 mium and zinc offer a prospect of this kind. 



This molecular change would probably be found to exist in large 

 masses of wrought iron as well as in the small specimens of wire 

 which I have examined, and would come into operation in various 

 cases where those masses are subjected to the conjoint influence of 

 heat and strain, as in various engineering operations, the destruction 

 of buildings by fire, and other cases. 



" On the Development of Electric Currents by Magnetism and 

 Heat/' By G. Gore, F.R.S. 



I have devised the following apparatus for demonstrating a rela- 

 tion of current electricity to magnetism and heat. 



A A, fig. 3, is a wooden base, upon which is supported, by four 

 brass clamps (two, B, B, on each side), a coil of wire, C ; the coil is 6 

 inches long, 1| inch in external diameter, and f of an inch internal 

 diameter, lined with a thin glass tube ; it consists of 1 8 layers, or 

 about 3000 turns of insulated copper wire of 0*415 millim. diameter 

 (or size No. 26 of ordinary wire-gauge) ; D is a permanent bar-mag- 

 net held in its place by the screws E, E, and having upon its poles two 

 flat armatures of soft iron, F,F, placed edgewise. Within the axis of 

 the coil is a straight wire of soft iron, G, one end of which is held 

 fast by the pillar-screw H, and the other by the cylindrical binding- 

 screw I ; the latter screw has a hook, to which is attached a vul- 

 canized india-rubber band, J, which is stretched and held secure 

 by the hooked brass rod K and the pillar-screw L. The screw H is 

 surmounted by a small mercury-cup for making connexions with one 

 pole of a voltaic battery, the other pole of the battery being secured 

 to the pillar-screw M, which is also surmounted by a small mercury- 

 cup, and is connected with the cylindrical binding-screw I by a cop- 

 per wire with a middle flattened portion O to impart to it flexibility. 

 The two ends of the fine wire coil are soldered to two small binding- 



