HALL. — ELECTRIC CONDUCTION AND THERMOELECTRIC ACTION. 103 



7. An Appendix gives data relative to change of volume and 

 change of electric resistance in the melting of metals. It is a general, 

 if not an invariable, rule that change of resistance in melting is of the 

 same sign as change of volume. An attempt is made at a quantitative 

 comparison of these two changes. 



8. Attention is called to the fact, first pointed out by Barus, that 

 in liquid mercury rise of temperature without change of volume 

 would bring a decrease of resistance. 



