22 



Mr. Carl Barus on the 



Table VII. — Pressure- Coefficient of Glass, surrounded by 

 Mineral Machine-oil. j? =150 atrn. 



Series No. 









Series No. 







i 



0. 

 It. 



10 3 k 

 SRfR. 



tip. 



krXW'. 



9. 

 R 



10 3 X 

 <m/K. 



dp. 



z>xio 6 . 



Mean k r X 10 6 . 









Mean k r X 10 6 . 









XI. 



61 



445 



137 



XL 



57 



400 



143 



215°. 



59 



420 



140 



215°. 



59 



400 



147 



80xl0 3 w. 









190xl0 3 o>. 









+138. 









+145. 









XL 



53 



425 



127 



XL 



71 



385 



185 



215°. 



67 



420 



157 



100°. 



94 



365 



260 



120xl0 3 w. 









30 x10V 



113 



375 



300 



+ 143. 









+250. 









XL 



41 



363 



115 



*xn. 



66 



395 



170 



310°. 



48 



415 



116 



215°. 



69 



395 



175 



f 6 x 10 3 w to 

 1 8 x10V 



46 

 52 



420 

 410 



112 

 126 



360xl0 3 w. 

 + 173. 



63 



355 



175 



+117. 



49 



48 



420 

 415 



117 

 115 





350 



155 



*xii. 



54 











310°. 



60 



350 



170 











26x]0 3 a>. 



67 



380 



180 











+168. 









* Another tube of higher resistance. 



Repetitions of this work led to virtually the same uniformity 

 of result, as is well evidenced by the close coincidence of the 

 data for 215°. The coefficients of the two tubes, however, 

 are not identical. A feature of Table VI. is the change of 

 sign of the pressure-coefficient, when the oil has become con- 

 taminated. It is in these experiments (Table VI.) that I 

 specially observed the apparent accommodation detailed in 

 §37. As a whole the data are in reasonable conformity with 

 Table I. 



18. My final experiments were made with a very sticky 

 mineral machine-oil (cf. § 1). Two tubes of the form fig. 3, 

 but of different resistances, were used (§ 17). 



At 310° the oil-coefficients are negative, whereas the glass- 

 coefficients remain distinctly positive. This seems to be a 

 conclusive test, since an effect of the glass in changing the 

 sign, or in any way increasing the oil-coefficients is incon- 

 ceivable. The increase of the latter with pressure at 215° 

 (cf. Table VIII.) is probably an actual occurrence. The two 

 tubes again differ in their properties. 



