TIIICKNKSS UF rOGOMl" I.IMESTONE. 4i) 



Chemistry shows no characteristic difference between this limestone sind 

 the older masses, the beds being more or less magnesian throughout their 

 entire vertical range. A complete analysis was made of a siliceous variet), 

 taken from near Wood Cone, yielding the following result : 



Silica ;i-345 



Alumina 0-300 



Ferric oxide 0-289 - 



Ferrous oxido 



Manganese 



Lime 50011 



Magnesia 0-535 



Water 0130 



Carbonic acid 39-111 



Phosphoric acid 0-240 



Chlorine 0030 



Organic matter Traces. 



Alkalies Traces. 



Total 100000 



To the east of Jackson Mine, where the beds are well exposed and lie 

 inclined at a nearly uniform angle, they measure 2,700 feet across tlieir 

 gi'eatest development. This thickness is probably surpassed by the beds 

 on the long spur south^^•est of Wood Cone, but there they stand nearly ver- 

 tical, in some places dipping eastward and in others westward, occasionally 

 shownng evidences of faulting, which prevents any reliable estimate of their 

 thickness. It is probable they measure over 3,000 feet. An estimate of the 

 strata at White Pine gives over 5,000 feet of limestone. At first sight it would 

 appear as if there mu§t have been some displacement of beds along Pros- 

 pect Mountain, but the succession of a rich fauna with tlie same character- 

 istic specific forms at the base and .summit of the epoch at both Eureka and 

 White Pine would preclude such a supposition and the simplicity and uni- 

 formity of structure go to show that such is not the case. 



Fauna of the Pogonip Epoch.— Throughout the entire thickness of the Pogo- 

 nip beds, organic remains characterize the epoch. At the base there is a 

 decided mingling of species, a number of Potsdam fomis extending up- 

 ward for some distance into the limestone. Passing upward, however, 

 these species gradually diminish and there comes in rajjidlv a numerous 

 fauna representing higher and higher forms, till midway in the beds nearly 



MON XX 4 



