114 Report of the State Geologist. 



until it is lost, but reappears at one-quarter of a mile farther and 

 increasing to 28 inches. This thickness was found at the Ogden 

 quarry, which was the first opened in the locality. 



Above this layer conies six feet of shale (" shuck ") ; then 4-16 

 inches of stone divisible in two to six layers, and then 20 feet 

 of shale, flying in fine pieces when blasted, which contains hard 

 streaks (not of much value) from one inch to two feet in thick- 

 ness. 



The marketable slabs are found of almost any length, and in 

 widths varying from 1 to 20 feet. The largest quarried here 

 was, Mr. King thinks, 12 feet 9 inches by 13 feet 9 inches, and 

 was used in the vault of a bank. The largest ever quarried by 

 him were three flags 9 feet 6 inches by 13 feet, which received 

 a premium at Philadelphia in 1876 for strength, texture, natural 

 surface and edges. 



A S. W. dip of one and one-half inches in 100 (three inches to 

 a rod) is found here and in other quarries for some miles to the 

 north. 



The joints are nearly vertical. A main joint runs ]^. 15° W. 

 (magnetic), but it recurs at very irregular intervals (6 to 40 feet), 

 and gives very varying dimensions to the slabs. No reliable 

 cross seam exists. Subordinate cleavages (" back seams ") tra- 

 verse the main joints in places, running about N. 10° W. extend- 

 ing not over 100 feet each way from the main seam. Back 

 seams are confined to the lower beds in the quarry. They are 

 well shown in the view. Much injury to the market worth of 

 the product is caused by their presence,. but they are fortunately 

 not common. 



Another form of objectionable cleavage is found, usually run- 

 ning parallel with the main joint, and limited to a few inches 

 (not over 20) in the thickness of beds. Between two main 

 seams that are, say 30 feet apart, there may be from one to ten 

 such, at from I to 10 feet apart. A whole block may be so cut 

 up that the widest piece is not over 20 inches across. 



Another source of injury is found in " burl," a formation of 

 concretionary' origin, whose presence is shown by saucer-shaped 

 protuberances and depressions and circular dif^ colorations.^ 

 Around the perimeters of burl the stone is of excessive hardness, 



♦ It turns brown against the greenish sandstone when weathered. 



