great Coal-field of Shropshire. 205 



first step of the ascent of Steeraway-hill) presents fragments of a bed 

 of limestone, between which protrude masses of coarse globular 

 greenstone ; then occurs a bed of sandstone slate, or flagstone, at an 

 angle of 35% which is succeeded by a bed of limestone elevated at 

 nearly the same horizontal angle ; then come four more beds at an 

 angle of 40°, being an alternation of sandstone and limestone, and 

 the last of these reaches to about two thirds of the ascent of the 

 hill ; the remainder, together with the summit, consists of amor- 

 phous and sienitic greenstone, covered with fragments of sandstone- 

 slate strata, the inclination of which, as far as can be ascertained, 

 approaches much more to horizontal than that of the preceding. 

 Although for the sake of brevity and clearness I have characterized 

 the above formation as an alternating series of four beds of sandstone 

 and limestone, yet it must be observed that each limestone bed con- 

 sists of several strata, each about a foot in thickness, composed 

 alternately of compact limestone and of bluish-grey clayey marl filled 

 with very delicate and brittle tubulites, the direction of the tubes 

 being perpendicular to the plane of the strata. 



An important geological question now occurs with regard to these 

 beds, which in their composition and in the general line of their di- 

 rection bear a close resemblance to the limestone of Wenlock Edge, 

 though they differ so greatly in the amount of their horizontal angle ; 

 are they or are they not in the position in which they were first 

 deposited ? The negative side of this question appears to be sup- 

 ported by the impossibility of a bed of sandstone, and much more of 

 clay marl (or mud as it no doubt was in its original state) being 

 deposited on a plane at an elevation of from SO' to 40% in such -a 

 manner as to constitute an extensive stratum of an uniform thick- 

 ness, and that hardly exceeding a foot, for a depth of at least one 

 hundred feet. The position also of the tubulites v/hich pierce 



