THERMAL CONDUCTIVITY OF OUARTZITE. 



Bv Prof. Ixoi'.KRT A. Leiifeldt, B.A.. D.Sc. 



In the course of an in\ cstit^alion connected with one of tlie 

 mines of the W'itwatersrand, I had occasion to examine the 

 thermal conductivity of the country rock, a quantity that ])lays 

 an important part in all (juestions of heating- and \-entilation of 

 The mines. 



I was sui)plied, through the kindness of the mine authorities, 

 with two samj)les of rejiresentative quartzite. about lo cm. scjuare 

 and between i and 2 cm. thick, with fiat ground and polished 

 faces. An apparatus was constructed, consisting of an electric 

 heater enclosed between thick copper plates, in the centre ; the 

 two specimen slabs on each side, and outside them two copper 

 tanks through which cold water was passed. The temperature 

 difference between the faces of the rock was taken by a pair of 

 thermojunctions embedded in narrow grooves cut in the copper 

 plates. The heat flow could be determined (a) by the current 

 through the heater, {b) by the inlet and outlet temperatures and 

 weight of water used in the tanks. (a) will slightly exceed 

 {b) on account of loss of heat from the edge of the rock speci- 

 mens. The mean value in a stationary state, combined with the 

 tem|)erature dift'erence, determines the conductivity. 



The experiment is easy and satisfactory : the most essential 

 precaiuion is to supply the cooling water from a constant level 

 apparatus, and at a constant temperature. 



The power used was from 20 to 40 watts ; the temperature 

 dilterence on the two sides of the rock 6° to 12°. The result ob- 

 tained was 



0.0388 watts ])er degree Cent, per cm. cube. 



The BoSKOP Skull.— At a meeting of the Manchester 

 Literary and Philosophical Society, held on the 23rd January, 

 JVofessor G. Elliot Smith discussed an endocranial cast obtained 

 from the fossil human skull, found near Boskop, in the Trans- 

 vaal, in 19 13, and submitted to him for report by Dr. L. Perin- 

 guey. Professor Elliot Smith declared that the capacity of the 

 cranial cavity must have been well above 1,800 c.c. — perhaps 

 even as much as 1,900 c.c. — greater than that of the skull of 

 Immanuel Kant, and almost equal to Bismarck's. The features 

 and certain other characteristics of the cast suggested affinities 

 with the Neauderthal race, but the larger size, and in particular 

 the ])refrontal l)ulging, indicated an even closer kinship with 

 Europeans of Aurignacian and later times. One conclusion that 

 emerges from a comijarison of such cranial casts is that it is 

 the size of the ])re frontal area rather than mere bulk that deter- 

 mines brain superiority. 



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