Niles.] 276 [April 5, 



been removed from the western side, leaving a north and south work- 

 ing face upon the western edge of this bed. The work now to be 

 done is to quarry the stone of that part of this bed which remains 

 in place at the eastern side of the quarry. If an easterly trending 

 -channel is now cut in this bed at the northern side of the quarry, for 

 example, the part of the bed south of it expands, causing a north- 

 ward movement of the edge of the rock forming the southern 

 boundary of the channel. If now another channel be cut in the 

 same bed parallel with the first but at some distance south of it, there 

 will be either no apparent movement of the rock north of it, or it 

 will be much less than that which followed the cutting of the first 

 channel, showing that the force has been partly or wholly expended. 

 But it may be asked, why should there ever be any movement at- 

 tending the formation of such a second channel? This occurs when 

 the bed so adheres to the one below it as to prevent its complete 

 expansion upon the formation of the first channel, hence another 

 becomes the occasion of an additional expansion. It makes no dif- 

 ference in the amount of movement whether the first channel in the 

 bed is made at the northern or southern side of the quarry; whenever 

 the stone is freed from the adjacent rock, the force expends its energy 

 in a northerly or southerly direction. It is also a significant fact 

 that when the beds are traversed by excavations which trend north- 

 erly and southerly, the force does not expend itself in an easterly or 

 westerly direction. It is only when the stone has opportunity for 

 expansion north or south, that the compressing power to which it is 

 subjected is fully exhibited. 



It is true that when a north and south channel has been cut in the 

 bottom bed of a quarry, fractures or movements have attended or 

 followed the operation. Such phenomena are observed at Monson, 

 where they are undoubtedly produced by the north and south pres- 

 sure only. In these instances the lateral east and west movements 

 of comparatively small portions of the rock are caused by the stone 

 yielding to the pressure in such a way that portions of it are bent or 

 thrown outward from the main bed in either an easterly or a west- 

 erly direction. 



I have not yet been able to continue my observations at Berea to 

 the extent to be desired, but at the present time I do not know of 

 any evidences of an easterly and westerly acting pressure. 



Such convincing evidence of the lateral compression of the rocks 

 of Berea, Ohio, by a force exhibiting the same characteristics, even 



