788 



W. G. FOYE 



2. Adams postulates that the elonga- 

 tion of the blocks occurred in the later 

 stages of batholithic intrusion as the 

 granite solidified. 



2. It would seem necessary that this 

 should be true; for a hot, fluid magma, if 

 too hot would melt the blocks and incor- 

 porate them into a homogeneous magma. 

 If it were too cold it could not elongate 

 them. The necessary conditions for the 

 production of parallel elongation, there- 

 fore, is a narrow temperature range 

 within which the blocks remain viscous. 

 This would be found, it would seem, at a 

 more or less constant distance from the 

 molar contact of the intruding batholith 

 with the country rock. As the magma 

 progresses upward, the central heat of 

 the batholith must likewise progress 

 upward and hence the parallel banding 

 of the batholith produced at any stage 

 would be destroyed in a later stage by 

 the complete solution of the blocks into 

 a homogeneous magma. The so-called 

 "batholiths" are in all stages of dis- 

 section yet the parallel structure is 

 persistent from center to edge. The 

 structure is not, therefore, a border 

 phenomenon as Adams' theory would 

 demand. 



3. Daly 1 has shown that limestone 

 blocks at high temperatures are much 

 heavier than fluid granite. Hence these 

 blocks should sink and leave a clear con- 

 tact which would be progressively 

 attacked by the hot granite magma. 

 This would not give rise to the parallel 

 structure observed. If, however, they 

 floated they would impede the attack of 

 the granite magma at the contact and 

 their solution or partial solution and 

 elongation would cause an enormous loss 

 of heat and render the further upward 

 progress of the batholith very difficult. 



It is estimated by Adams and Barlow that 20 per cent of the 

 "batholithic" areas consist of gray gneiss and amphibolite. This 

 estimate is low for the districts visited by the writer. Not only 

 these rocks but also bands of pure limestone are often found near 



3. The limestone blocks, stoped from 

 the roof of the granite batholith, floated 

 and so were elongated by the movements 

 of the granite parallel to its contact. 



l Igneous Rocks and Their Origin (1914), 202. 



