CANANDAIGUA AND NAPLES QUADRANGLES 13 



the amount of chert is not too large, is compact and durable and 

 exceedingly valuable as building stone and for the production of 

 quicklime. If the chert is entirely absent the liiaestone is easily 

 quarried and makes very handsome dark gray cut stone building 

 material, and the cherty masses have been extensively worked for 

 bridge abutments, canal locks, retaining walls and kindred pur- 

 poses. 



This formation covers a belt 1 to 3 miles wide across the towns 

 of Mendon, Victor and Farmington and some exposures of the 

 uppermost beds occur also in Canandaigua. The more striking 

 outcrops of the rock and those which have long been most avail- 

 able for exploitation are in the region just to the east, specially 

 in the towns of Manchester and Phelps. In a general way it may 

 be stated that at the base of the formation there are from 3 to 5 

 feet of limestone, very rich in corals and without any chert. 

 The rest of the formation which attains a total thickness of about 

 120 feet has both chert and shaly layers scattered through the 

 limestones at irregular intervals. 



In Farmington the lower beds crop out on the north side of the 

 road leading from Manchester to Victor and have been extensively 

 quarried, the stone used in the construction of the Erie canal 

 locks at Macedon having been obtained from this locality. 



In the bed of Mud creek the base of the formation appears about 

 GO rods below the railroad bridge at Mertensia, in a low anticline, 

 the axis of which crosses the stream diagonally. Here it rests 

 on the Oriskany sandstone and the lower 5 feet are free of chert 

 and are crowded with corals, the stratum being identical in 

 character and appearance with the basal layer farther east. 

 These layers are capped by a series of chert-bearing beds, together 

 aggregating 5 feet in thickness. Above the bridge there is an 

 extensive picturesque cascade and an exposure of 40 to 50 feet of 

 the middle and upper beds, the outcrops extending though not 

 continuously, 100 rods south of the cascade. The rock at this 

 pla(!e has been Avorked for construction stone. 



In the section ahuig Great brook or Hog hollow at Victor the 

 lower layers appear overlying the Oriskany and at this point the 



