40 BULLETIN OF THE NATURAL HISTORY SOCIETY. 



This lateral pressure has heen shown to exist at 

 Monson, Mass. In the (j^uarry at that place it has been 

 found that after the removal of a block of stone, the 

 rock on each side of the space from which this block 

 was taken, would, in the course of a few hours, creep 

 together considerably, showing that there was a tension 

 of the rock in this quarry, indicating a pressure from the 

 south, ^ The well-known case of the flexures on a 

 gigantic scale in the Carboniferous and pre-Carboniferous 

 rocks of the Alleghan}" ranges show that such a pressure 

 has been in active operation from a south-east direction 

 in the middle states since the Carboniferous period. 

 The prevailing south-east dip, and the numerous 

 monoclines, dipping in that direction, among the pre- 

 Carboniferous rocks of Southern ]^ew Brunswick, all 

 point to the former action for intense pressure from the 

 south-east. And it seems probable that the continued 

 ..action of the force, to which this pressure is due, in a 

 milder form, is responsible for uplifts on the south side ot 

 these pre-glacial faults. 



The force which has produced those i)()st-glacial faults 

 appears to correspond in its action to that which caused 

 the tension in the Monson quarry, only that in the case 

 of the St. John locality it seems to liave operated from a 

 somewhat difl:erent direction. At St. John the greatest 

 throws, and the most frequent, have a north-east to south- 

 west course, and the more the joints depart from this 

 course the less is the rock on their sides displaced ; so 

 tliat at right angles to this course a fault is quite rare. 



* The above was written from memory. I tbink tbe "Phenomena observed in 

 quarrying." by Prof. W. H. Niles, described in American Journal of Science, March' 

 1872, refers to this occurrence. Among other peculiarities it was mentioned that a 

 block split off with wedges 354 feet long, eleven feet wide, and three feet thick, freed 

 at one end, but not at the other, was observed soon after being split to have 

 lengthened one inch and a half ; the expansion was not due change of temperature- 



