276 E. W. Morley — Volumetric Composition of Water. 



The detailed stratigraphy of the dark, coal-bearing shales 

 immediately beneath the Redroek sandstone is exposed a short 

 distance below the village of Redroek. The coal seam is from 

 four to five feet in thickness ; and is overlain in places by a 

 few feet of alternating sandy and clayey shales. In the sand- 

 stone directly over the coal are vast numbers of finely preserved 

 vegetable remains : huge lepidodendrids and sigillarids of 

 eight, ten or more species, massive calamites and delicate 

 ferns, abundant but not packed together in confused masses. 



The recent observations have cleared up many of the hitherto 

 doubtful points concerning the geological history of the Red- 

 rock sandstone. It is not the basal member of the Coal- 

 measures, as was regarded by Worthen ; noi is it a shore ex- 

 tension of the Kaskaskia limestone; neither is its geographic 

 extent as limited as had been supposed. Twenty miles to the 

 southeast of Redroek a sandstone of great thickness, having 

 identical lithologic characters and with a similar strati- 

 graphical position is believed to be its extension southward. 

 And it may also rise a few feet above low-water in the north- 

 western corner of Marion county. The most interesting 

 consideration in regard to this Redroek sandstone is the fact of 

 its considerable elevation above the surface of the sea and its 

 subjection to subaerial erosive agencies for a long period of 

 time before submergence again took place. During that 

 interval the great thickness of sandstone probably was almost 

 entirely removed in places. 



The southern prolongation of the formation yet remains to 

 be made out and its geographic limits eastward and westward 

 from Redroek village more definitely determined, for there is 

 every reason to believe that it extends beyond the boundaries at 

 present known. 



Art. XXXI. — The Volumetric Composition of Water • by 

 Edward W. Morley. 



[Continued from page 231.] 



Apparatus for accurate measurement of volumes of 

 Gases. — My measuring apparatus has finally become rather 

 elaborate. It is shown in fig. 3. It is mounted on a stone 

 pier, independent of the floor of the room in which it stands. 

 The eudiometer and measuring tube ends above in a stopcock 

 and recurved tube whose end is seen to emerge inside the left 

 hand gas jar in the cistern. The stopcock is manipulated by 

 means of a metal shaft and long handle, seen at the top of the 

 column which carries the reading microscope. At the bottom 



