222 Tlie Irish NatiDulist. November, 



of heat froui the surface. Hence the heat escaping from the 

 earth cannot be taken as a measure of the radium within. 

 Yet the earth has probably reached the stage when the loss of 

 its heat is balanced by that supplied by radium, and when its 

 future cooling depends on the decay of the uranium within, 

 and the consequent diminution in the supply of fresh radium 

 to the mass. An examination of the proportions of radium 

 in the rocks from the St. Gothard and Simplon tunnels shows 

 that the abnormalities of temperature in these tunnels are 

 related to the radium localh' present. The next section of 

 the address dealt with the effect of the accumulation of sedi- 

 ments, naturally containing uranium and radium, on the 

 temperature of the underlying crust. A weakening of this 

 part of the crust must result through the rise of temperature 

 towards the base of the deposit, and it w^ill hence jdeld to 

 stresses readily. The sedimentary region, commonly of a 

 band-like form, will then become bulged up into a mountain- 

 chain, a fact which is well knowm to occur in geological 

 history. Since the rise of temperature at the base of a deposit 

 is proportional to the square of the thickness of the deposit, 

 it by no means follows that sediments, such as deep-sea red 

 clays, of high radio-activity, are as effective in promoting crustal 

 movements as others of less radio-activity but greater thick- 

 ness. Prof. Joly's address appears in full in Nahwe for 

 September loth, 1908. 



The whole subject connecting radium and temperature 

 being only five 3'ears old, it is remarkable that conclusions 

 of such high interest should alrcad}^ be forthcoming. Prof. 

 Joly does not conceal the assumptions made when he comes 

 to calculations : but the mere comparative measures, obtained 

 with considerable labour, offer a sound basis for future 

 dissertations. 



The second distinctive feature of this section was the dis- 

 cussion that was arranged on Mountain-building, in which 

 the President also took part. Here, again, heating due to 

 radio-active bodies was brought into play. Since recumbent 

 folds and nappes de rcco^ivrevicnt absorbed much of the attention 

 of the speakers, Sir A. Geikie usefully pointed out the for- 

 mation of certain mountains by block-faulting, without con. 

 spicuous folding. Prof. Lapworth gave what was practicall}' 



