374 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1908. 



activities observed; but "as a different distribution of radium may, of 

 course, obtain below our point of observation, the result can only 

 claim to be suggestive. 



Turning specially to the St. Gothard, we find that a temperature 

 problem of much interest arises from the facts recorded. The north 

 end of the tunnel for a distance of 2 kilometers traverses the granite 

 of the Finsteraarhorn massif. It then enters the infolded syncline of 

 the Usernmulde and traverses altered sediments of Trias-Jura age for 

 a distance of about 2 kilometers. After this it enters the crushed and 

 metamorphosed rocks of the St. Gothard massif, and remains in these 

 rocks for 7^ kilometers. The last section is run through the Tessin- 

 mulde for 3 kilometers. These rocks are highly altered Mesozoic 

 sediments. 



I have alreadj^ quoted Stapff's observations as to the variations of 

 gradient in the northern, central, and southern parts of the tunnel. 

 He writes: "They (the isotherms) show irregularities on the south 

 side, which clearly depends on cold springs ; they bend downi rapidly, 

 and then run smoothly inclined beneath the water-filled section of the 

 mountain. Other local irregularities can be explained by the decom- 

 position of the rock ; but there is no obvious explanation of the rapid 

 increase 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 differ- 

 ent thermal qualities of the rock on the coefficient of increase. For the 

 rest these 2,000 meters of granite belong to the massif of the Finste- 

 raarhorn, and, geologically speaking, ihej do not share in the com- 

 position 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." 

 (Loc. cit., p. 30.) 



Commenting on the explanation here offered b}^ Stapff, Prestwich " 

 states his preference for the view that the excess of temperature in the 

 granite is due to mechanical 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 remembered that the increase in 

 radio-activity shown at the south end would have been, according to 

 Stapff, masked by water circulation, the correspondence becomes the 

 more striking. The small radium values in the central parts of the 

 tunnel are remarkable. The rocks of the Central St. Gothard massif 

 are apparently exceptionally poor in radium. 



At the north end the excess of radi' .i is almost confined to the 

 granite, the .ack to which Staj^ff asc ted the exceptional tempera- 



« Proc. Roy. Soc, \" ... XLI, i>. 44. 



