Kinetic Theory of Solids. 221 



Temp. C 18° 65° 103° 



nj. 2-87 2-74 2'65 



n 2 2-50 2-35 2-17 



10' 6 q 220 198 178 



n\-n\ 1'99 1*99. 2-31 



The theoretical value of n\— n\ according to equation (D) 

 is 2*02, so that the formula is well verified in this case. 



Magnesium. — Fine commercial wire, as used in rigidity 

 experiments. I 43'9 cm., m *201 grm., p 1*74. 



Temp. C 17° 68° 104° 



n x 2-09 2-05 1-97 



n 2 1-62 1-57 1-54 



1O" 6 352 335 314 



n\-n% 1-75 1'74 1-51 



The theoretical value of n\—n\ is 1*75. It is to he re- 

 membered that in the case of the metals, n^—n 2 ^ which measures 

 the effect of gravity as compared with that of elasticity, is very 

 small, and that on account of experimental errors only general 

 agreement in magnitude is to be expected between the ex- 

 perimental and theoretical values of n\— n\. For example, the 

 discrepant experimental number 1*51 just given illustrates the 

 amount of departure that may occur. 



Zinc. — The thin rod prepared for the Rigidity experiments. 

 I 63*5 cm., m 31*3 grm.,/? 7*04. 



Temp. C 16° 60° 103° 



n x 3-53 3-40 3'21 



n 2 3-24 3-11 2*97 



10~ 6 q 821 758 682 



n\-n\ T96 1'89 1-48 



The theoretical value for n\—n\ is 1*21. 

 Copjjer. — Swedish wire for alloying gold. I 63*5, m 22*4, 

 p 8-95. 



Temp. C 16° 102° 



n x 3-11 2*98 



n 2 2-92 2*79 



10-tq 1378 1260 



n\-n\ 1-14 1-10 Theory 1-21. 



