712 



SCIENCE 



rN. 8. Vol. XXVIII. No. 725 



inclined beneath the water-filled section of the 

 mountain. Other local irregularities can be ex- 

 plained by the decomposition of the rock; but 

 there is no obvious explanation of the rapid in- 

 crease in the granite rocks at the northern end 

 of the tunnel (2,000 meters), and it is probably 

 to be attributed to the influence of different ther- 

 mal qualities of the rock on the coefficient of 

 increase. For the rest these 2,000 meters of 

 granite belong to the massif of the Finsteraar- 

 horn, and, geologically speaking, they do not share 

 in the composition of the St. Gothard. Perhaps 

 these two massifs belong to different geological 

 periods (as supposed for geological reasons long 

 ago). What wonder, then, if one of them be 

 cooler than the other." 



Commenting on the explanation here of- 

 fered by Stapff, Prestwich^^ states his 

 preference for the view that the excess of 

 temperature in the granite is due to me- 

 chanical actions to which the granite was 

 exposed during the upheaval of this region 

 of the Alps. 



The accompanying diagram shows the 

 distribution of temperature as given by 

 Stapff, and the distribution of radium as 

 found from typical specimens of the rocks. 

 There is a correspondence between the two 

 which is obvious, and when it is remem- 

 bered that the increase in radio-activity 

 shown at the south end would have been, 

 according to Stapff, masked by water cir- 

 culation, the correspondence becomes the 

 more striking. The small radium values in 

 the central parts of the tunnel are remark- 

 able. The rocks of the Central St. Gothard 

 massif are apparently exceptionally poor 

 in radium. 



At the north end the excess of radium is 

 almost confined to the granite, the rock to 

 which Stapff ascribed the exceptional tem- 

 peratures. The radium of the Usernmulde 

 is probably not very important, seeing that 

 these sediments can not extend far down- 

 wards. The principal local source of heat 

 appears located more especially beneath the 



" Loc. cit., p. 30. 



^'Proc. B. S., XLI., p. 44. 



synclinal fold, for Stapff 's table {loc. cit., 

 p. 31) of the gradients beneath the plain of 

 Andermatt shows a rising gradient to a 

 point about 2,500 meters from the north 

 entrance of the tunnel. It is observable 

 that the radio-activity of the granite in- 

 creases as it approaches the Usernmulde 

 and attains its maximum (14.1) where it 

 dips beneath the syncline. 



The means of radium-content in the 

 several geological sections into which the 

 course of the tunnel is divisible are as 

 follows : 



Granite of Finsteraarhorn 7.7 



Usernmulde 4.9 



St. Gothard massif 3.9 



Tessinmulde 3.4 



The central section, however, if con- 

 sidered without reference to geological 

 demarcations, would, as already observed, 

 come out as barely 3.3. And this is the 

 value of the radio-activity most nearly ap- 

 plicable to Stapff 's thermal subdivision of 

 the region of low temperature. 



If we accept the higher readings ob- 

 tained in the granite as indicative of the 

 radio-active state of this rock beneath the 

 Usernmulde, a satisfactory explanation of 

 the difference of heat-flow from the central 

 and northern parts of the tunnel is ob- 

 tained. Using the difference of gradient 

 as basis of calculation, as before, we find 

 that a downward extension of about six 

 thousand meters would, if the outflow took 

 place in an approximately vertical direc- 

 tion, account for the facts observed by 

 Stapff. This depth is in agreement with 

 the result as to the downward extension of 

 the St. Gothard rocks as derived from the 

 comparison with the Simplon rocks. 



We are by no means in a position to 

 found dogmatic conclusions on such re- 

 sults; they can only be regarded as en- 

 couragement to pursue the matter further. 

 The coincidence must be remarkable which 

 thus similarly localizes radium and tem- 



