MURPHREE'S VALLEY; ECONOMIC GEOLOGY. 75 



the S. E. i of the S. E. it sinks beneath the surface. The 

 upper bed of iron ore was found on this tract, about the 

 same thickness and quality as in Sec. 23. 



At the point where the last of the Clinton passes beneath 

 the surface, a new member, not heretofore seen in this val- 

 ley, is largely exposed. It is the Keokv.k Limestone of the 

 Lower Siliceous formation. It is here, at once a heavy 

 member, and though its geological relations cannot be seen 

 here, yet it continues into section 27, where its relations are 

 clearly seen. This member might, from its appearance, be 

 yen- readily mistaken for the Carboniferous or Mountain 

 Limestone and if seen only at this point, would be so re- 

 garded, even by sharp-eyed geologists. But when traced 

 farther its position is seen to be beneath the LaGrange or 

 Oxmoor Sandstone, and just above the Biack Shale, and 

 hence a member of the Lower Siliceous group its lowest 

 member. It is here a very pure semi-Crystalline limestone 

 about 100 feet thick. 



On entering Sect. 27 in the N. -i- of the N. E. J we pass 

 directly from the top of the Keokuk Limestone on to the top 

 of the Clinton the former having been lapped over on the 

 latter, for the last half mile. The Clinton is here in a high 

 narrow ridge. Some iron ore of good quality is seen in it. 

 belonging to the 1st and 2nd beds, but the quantity is incon- 

 siderable. The ridge has the appearance of being princi- 

 pally made up of Clinton strata, and the distance from the 

 1st ore bed to the first Cambrian Limestone, is over 200 feet. 

 This with a dip of 45 C would give it a thickness of over 100 

 leet. But no other beds, or fragments from them, could be 

 found. It is probable that the Limestone comes much closer 

 here than it appears to do, and that it is covered over by 

 debris from the Clinton. This is seen to be the case 200 

 yards to the S. W. The Clinton here becomes very narrow 

 not more than 50 feet thick, and in the S. W. of the N. E. 

 i it is yet much thinner. A stream cuts through it (the 

 Wade Gap stream) near this, or in this tract. The rocks 

 are exposed, and gave the following section, as measured at 

 right angles with the strike : 



