()2 PROCEEDINGS OF THE AXX ARFJOK MEETINCJ 



has been accorded it. It seems to bear a irieat resemblance to the theory of 

 W. H. Piekerinjr. published a ijood many years ajro in the Journal of Geoloj;:y. 



Trof. A. r. Coi.EMAX : Professor Daly shows a poetic imagination in his 

 theory of the shifting; of continents for thousands of miles, crowding the ed^es 

 into mountain ranges: but if we admit that isostatic eiiuilibrium is nearly 

 l»erfect. there must have been a corresponding flow of the underlying plastic 

 stratum foi" the same distance in the opposite direction. 



Trof. J. A. Uddex : I should like to inciuire why it is necessary to suppose 

 that there is a glassy zone at certain distance below the crust. To my mind, 

 such a zone is not necessary to permit flowage. 



Remarks were made also by Messrs. A. C. I.awson, J. L. Rich, H. M. 

 Ami. and II. S. Washino-ton, with rej)ly hy the author. 



oiiodEMc i:m(!i:\('ii:s of a ho'iahy j:.\r'ih 



r.Y CllAKI.KS KKVKS 



{Abstract ) 



Since the hypothesis of isostasy is really a nudtiple one and resolves itself 

 into no less than four distinct hypotheses, it becomes obligatory to determine, 

 not from simple mathematical figuring but from calculation and observation 

 in the field, the position of the geological directrix. Assumption of sealevel as 

 a basis is obviously illogical and entirely unsupported by observation : but the 

 liocky Mountains in their repeated waxing and waning point to the position 

 of an isostatic datum at about two miles below sealevel as a possible proper 

 l)asis for calculation. Isostatic compensation appears to be an orogenic effect 

 and not a cause; and there may be explanations for the same phenomena other 

 than isostasy. 



Further experimentation along lines reported several years ago (Kulletin. 

 :>()-7(>. 11)19) emphasizes the function of retardation of the earth's rotation as 

 a primary cause of orogenic disturbance in the globe's straticulate crust. It 

 does not seem necessary to premise permanency of oceanic basins or of conti- 

 nental i»laits. 



\\v'm\ hy title. 



ISOSTASY AS A /.'/v.sT/.V O/' KAh'TIl Sll l{ I \ KAGh: 

 in IKA.XCIS PAKKKK SIIKPAllD ' 



{Abi<trart) 



Opposition to the theory of isostasy is directed primarily against geological 

 interpretations of the theory ratlu-r than against the geodetic conclusions. 

 Changing these interpretations of the working of isostasy might make it more 

 compatible with the phenomena of geology. Isostasy could be as effective in 

 ki'cping the crust balanced with a shrinking interior of the earth as with nou- 

 shrinking interior. Mountains due to a shrinking interior would tend to keep 



» Introduced by T. T. Quirke. 



