ABSTRACTS OF PAPERS 0< 



A LAYMAX'!^ VfEW OF THE THEOHY OF rsOSTASY 

 BY C. K. LEITH 



(Ahstrac-t) 



All attempt to discriminate the kiiowu facts of isostasy from, tlie various 

 assumptions which have entered into the* tlieory as now liiiown, and a discus- 

 sion of some of these assumptions from tlie standpoint of structural geology. 



Read from manuscript. 



Discission 



Mr. I). F. HiGGiNS : Geologists should not confuse the terms '"stress" and 

 "strain." In the engineering (physical) sense, stress is a force, strain is a 

 change of shape. To avoid the ambiguity in the word strain, it is better to 

 avoid it altogether and use the word deformation in its stead. 



As far as the Rocky Mountain Front Range of Colorado is concerned, I'ro- 

 fessor Leith's statement that the hearts of the great ranges are granitic does 

 not hold. The Front Range is essentially sedimentary (Precambrian ). into 

 which have been intruded the relatively small granite batholiths of Long's 

 Peak to IMkes Peak, for example. 



The assumption of a primordial earth of uniform (initial) density is not in 

 accord with the postulates of the IManetesimal Hypothesis. The Fellows of 

 this Society know how the differences of density, established by competent 

 geodetic observations, may be invoked at present to bring about, in part at 

 least, the changes of elevation necessary for the erosioiial cycle, and hence how 

 they may have started the isostatic-erosional cycle at first. The postulatioii 

 of an earth of initial uniform density, subject only to stresses due to contrac- 

 tion on loss of heat, would not lead to any but very slight deformation due to 

 the fact of isostatic adjustment. 



Mr. T. I*. Shepaku : I'rofessor Leith's statement that the mountain ranges 

 are lightened by katamorphism is opposed by the fact that the light katamor- 

 phic material from the mountain ranges is removed by erosion and redeposited 

 on the bordering plains, leaving denser material on the mountains and less 

 dense on the plains. 



Remarks were made also b}' Mr. William Bowie. 



RECTJLIXEAR SHORELIXES OF THE XEW EXOLAND-ACADIAX REGIOX 



1:Y DOIGLAS W. JOHXSOX 



{Ahstruct) 



Many rectilinear shorelines bordering parts of New England and Acadia 

 have been attributed to faulting. The paper discusses a variety of ways in 

 which rectilinear shorelines are produced, and shows that many such coastal 

 lineaments in the region in question, attributed to faulting, are better ex- 

 plained as the result of other processes. 



Read bv title in absence of author. 



