ELECTEICAL RESISTANCE UNDER PRESSURE. 153 



ment. In particular the factor of atomic arrangement is responsible 

 for the difference between a solid and a liciuid metal, and may be so 

 important in some cases as to control the sign of the effect. 



Summary. 



In this paper results are given for the effect of pressure and tempera- 

 ture on the resistance of twenty elements and several alloys. Endeavor 

 was made to choose elements from unusual places in the periodic 

 table, and also to investigate more fully the behavior of liquid metals. 



The resistance of the same metal in the liquid and the solid state 

 has now been measured for six elements. The temperature coefficient 

 of the liquid is less than that of the solid except for potassium. The 

 change of resistance on melting invariably follows the direction of the 

 change of Aolume. The ratio of resistance of liquid to solid is approxi- 

 mately constant along the melting curve, although the difference of 

 volume may change greatly. The pressure coefficient of the liquid is 

 in some cases less than that of the solid. Liquid bismuth has a nega- 

 tive pressure coefficient of resistance, and is normal, but liquid lithium 

 has a positive coefficient, and is the only such liquid metal yet found. 

 The new liquids do not show a negative temperature coefficient of 

 resistance at contant volume, as did Uquid mercury. 



The alkali metals sodium and potassium are remarkable for the 

 large changes of resistance under pressure. The pressure coefficient 

 decreases greatly with increasing pressure, and decreasing temperature. 

 The temperature coefficient may decrease greatly with increasing 

 pressure. The variations of these coefficients for the metals in\ esti- 

 gated in the previous paper were always small. 



Three more solid elements have been found with positive pressure 

 coefficients of resistance; lithium, calcium, and strontium. Of these 

 the pressure coefficient decreases with increasing temperature, the 

 temperature coefficient decreases with increasing pressure, and, except 

 for strontium, the pressure coefficient increases with increasing pres- 

 sure. 



Of the non-metallic elements, black phosphorus is remarkable for 

 a very large negative coefficient, the resistance under 12000 kg. drop- 

 ping to only 3% of its initial value; silicon has a negative coefficient 

 which becomes numerically larger with increasing pressure, and 

 carbon has a negative coefficient in the amorphous state, and a posi- 

 tive coefficient in the graphitic state, which decreases greatly with 

 increasing pressure. 



