of the Rocks of the Loetschbevy Tunnel. 409 

 Table I \. 



Distance from R d' m 



North Portal Nature of Rock. ^ * ' . 

 iu metres. 



0415 Granite 28 



6120 Ditto 2-5 



5715 Ditto 29 



5160 Ditto 2-3 



4345 Ditto 20 



4235 Ditto 2-1 



4200 Aplite 2*5 



4180 Ditto 25 



4010 Quartz Porphyry 2'5 



3978 G-ranite 13 



3965 Limestone 15 



3945 Ditto 1-6 



3938 Ditto 1-5 



3935 Anhydrite 1'0 



3885 Limestone 15 



3870 Ditto 16 



3850 Ditto 1-5 



3810 Schist 2-9 



3761 Anhydrite 1*2 



3755 Limestone 14 



3740 Ditto 2-0 



3715 Black Schist 2'8 



3640 Quartz Sandstone 43 



3600 Black Schist 28 



975 Limestone 1*1 



760 Ditto 1-2 



725 Ditto 09 



"640 Ditto 1-5 



540 Ditto -.- 2-9 



175 Limestone P8 



90 Ditto 1-0 



It will be seen from Table I. that, as previously mentioned, 

 there is no very striking variation in the radium content as 

 we proceed along the tunnel. The northern end of the 



tunnel is the poorest in radium, and there is not much 

 difference between the mean radium content for the central 



section through the Gastern Grauite and the south end, 

 where schists are mostly met with. We would naturally 

 expect the northern end through the Jurassic Limestone to 



be the poorest, as all previous investigators have found that 

 calcareous rocks contain, on the whole, the smallest quantity 

 of radium. 



