58 Mr. H. H. Poole on Thermal Conductivity and Specific 



In the same way equations (11) and (12) would be uni- 

 versally true and would correspond to the theory of the 

 constitution of matter given by Larmor and Lorentz. 



The difference between the various schemes (A), (B), (C) 

 is really only one of the definition of the vectors, and no 

 experiment can, since all are consistent with the theory of 

 relativity, decide what definition is to be considered correct. 



V. On the Thermal Conductivity and Specific Heat of Granite 

 and Basalt at High Temperatures. By Horace H. Poole, 

 M.A., B.Sc* 



IN a previous paper (Phil. Mag. July 1912) a description 

 was given of some experiments on the thermal con- 

 ductivities of limestone and granite at high temperatures. 

 The method adopted consisted in generating heat electrically 

 along the axis of a cylinder of rock which is enclosed in a 

 tube electric furnace maintained at a constant temperature, 

 and measuring the difference of temperature between thermo- 

 junctions cemented in grooves cut at two distances from the 

 axis. The results indicated a considerable fall of conductivity 

 with rise of temperature in both cases. This fall was partly 

 of a permanent nature due probably to a development of 

 porosity in the limestone owing to escape of carbon dioxide, 

 and to minute cracks in the granite. Both rocks showed signs 

 of alteration, the granite being lighter in colour and much 

 softer after heating. In addition to the permanent fall of 

 conductivity there was a temporary fall at high temperatures, 

 the conductivity rising again when the temperature was 

 reduced. The determinations were carried up to 366° C. in 

 the case of the limestone and 537° 0. in the case of the 

 granite. 



In continuing the work it seemed to be desirable to make 

 determinations on rock cylinders of greater ratio of length 

 to diameter with a view to reducing possible end errors, 

 accordingly the dimensions of the apparatus were modified. 

 A new tube-furnace was constructed similar to the one 

 previously described, except that the copper tube is longer 

 and narrow-er — 47 cm. long by 3*8 cm. in diameter. The 

 furnace was laid horizontally. The heating element is com- 

 posed of nichrome ribbon put on in tw 7 o equal circuits, which 

 can be joined either in series or parallel to facilitate the 

 control of the temperature. This arrangement was, how- 

 ever, rendered unnecessary by the use of two transformers, 

 * Communicated "by the Author. 



