THE MOLECULAR RESPONSIVENESS OF MATTER 5 



wire, and if its molecular condition be the same throughout, 

 it is obvious that its physical properties will likewise be 

 uniform. Hence its electrical condition will also be the 

 same at every point ; in other words, it will be iso-electric. 

 But if a portion of this wire should now be made to undergo 

 a molecular change, as, say, by hammering, the physical 

 condition of this portion will be made different from that of 

 the rest. There will, therefore, be an electrical difference, 

 and the wire will no longer be iso-electric. This fact can 

 be verified by making suitable connections between the 

 molecularly strained and unstrained portions of the wire, 

 and a galvanometer, when a current will be found to flow 

 through the galvanometer, showing that a difference of 

 electrical potential has been brought about by the induced 



f 



TWII\ : 



VB 



FIG. 6. Electric Response in Metals 



(a) Method of block ; (b) Equal and opposite responses when the ends A 

 and B are stimulated ; the dotted portions of the curves show recovery ; 

 (c) Balancing effect, R, when both the ends are stimulated simultaneously. 



inequality of molecular conditions in different parts of the 

 same wire. 



I shall now describe the method by which electrical 

 responses to molecular disturbance may be obtained from 

 inorganic substances. For this purpose, two different methods 

 may be employed first, the method of block, and, secondly, 

 the method of relative depression. According to the first 

 of these, the wire to be experimented on is held clamped 

 at the middle, electrical connections being made with a 

 galvanometer at two points, A and B, by means of two 

 non-polarisable electrodes (fig. 6). We may now produce 



