309 



an inch in thickness, while in the thicker layers of the breccia 

 fragments an inch or more in thickness occur. 



''During the summer of 1895, when making observations 

 on the flats exposed at low tide in the inlet west of Noyes 

 Point, Rhode Island, I noticed that when the tide went out 

 before daylight the layer of fine sand and mud exposed to the 

 dry wind and sun during the day hardened, and that when 

 the surface of the water of the incoming tide was broken by 

 small waves the hardened layer was lifted, broken into 

 angular fragments, and piled in some places to a depth of 

 several inches, while in other places it was simply turned over 

 and was very little disturbed. When much disturbed the 

 edges of the fragments were rounded, so as to give them the 

 appearance of having been rolled a considerable distance. In 

 one instance the ensuing outflowing tide deposited a thin 

 layer of sand and silt over the breociated fragments. From 

 these observations it is evident that should the same 

 phenomena occur on a sinking shore-line, breccias of this 

 character, so often met with by the field geologist, would be 

 formed. "(21) (As an illustration of this process see plate 



XX.) 



Classification. 



Many of the terms used by the respective authors, quoted 

 above, evidently have a common application and must be 

 taken as synonyms. It appears possible to divide the various 

 deformations into two classes based on a question of time, 

 whether contemporaneous with the deposition of the beds 

 or as occurring at a later o-eolo^ical stao-e. In the former 

 case the beds became broken and deranged before a final 

 consolidation took place; and, in the latt-er, the beds had 

 reached a high degree of induration before disruption. 

 Another principle of classification can be based on the nature 

 of the agency which was responsible for the deformation, 

 whether chemical or dynamical. On such lines the following 

 classification has been attempted, utilizing such terms as have 

 been introduced into the subject by other authors, so far as 

 they suit my purpose : — 

 I. Syngenetic (Contemporaneous deformations). 

 1. By contraction in drying: — 



(a) Desiccation Breccias and Conglomerates 



(Hyde, 1908). 

 (h) Endolithic Brecciation (Grabau, in part, 



1913). 

 (c) Intraformational Breccias (Grabau, 1913). 



(21) Walcott, "Camb. Rocks of Pennsylvania," Bull. U.S. 

 Geolog. Sur., No. 134 (1896), p. 40, pi. xv. 



