ANNIVERSARY ADDRESS OF THE PRESIDENT. 175 



limestone at Windsor Mr. Lyell describes as " a lower carboniferous 

 limestone." The total vertical thickness of the coal-measures is 

 more than double that of the South Wales section, being 14,570 

 feet. 



a. The number of distinct beds in the section, of which separate mea- 

 surements are given, is 1114, from six inches to 138 feet thick, without 

 change in mineral composition. 



h. These beds consist of quartzose sandstones, grits and conglomerates, 

 and of arenaceous and argillaceous shales, all of various shades of red, grey, 

 and green, without any apparent order of succession, sometimes one some- 

 times another lying upon the coal, and occasionally a carbonaceous shale 

 is associated and iatermixed with the coal-seams. 



c. Interstratified with these beds are seventy -six seams of coal, from an 

 inch to two feet thick, the far greater proportion very thin. The aggregate 

 thickness of the seventy-six seams is only forty-four feet, and there is about 

 the same aggregate thickness of carbonaceous shale. The highest seam is 

 covered by a series of beds of sandstones, conglomerates and shales, 2274 

 feet thick. Beneath the lowest seam of coal there are 2800 feet of sand- 

 stones and shales of the same nature as those above, but having numerous 

 beds of grey concretionary limestone intercalated. Thus the coal-hearing 

 strata have a thickness of about 9500 feet, 



d. There are no terms attached to the word "Coal" indicating any 

 change of quality throughout the section. Some of the seams are called 

 '* Coaly clay," others " Carbonaceous shale" mixed with the coal. The 

 seams occur at very unequal distances ; from a few inches apart to more 

 than 1200 feet. 



e. As in the South Wales section, the coal-seams usually rest on beds 

 containing StigmaricB, but, in a great proportion of instances, these occur 

 not in clay but in sandstone and arenaceous shale. This under bed is from 

 a foot to twenty- seven feet in thickness ; in one place an understone with 

 StigmaricB ten feet thick has a seam of coal over it only an inch thick. 



/. Between the sixty-seventh and sixty- eighth coal-seams, the former 

 with associated carbonaceous shale only fourteen inches thick, there are 

 170 beds of sandstone and argillaceous shale, from six inches to 132 feet 

 thick, their aggregate thickness being 2620 feet, and the sixty- eighth coal- 

 seam is only called coaly clay, two inches thick, with an underclay con- 

 taining Stigmaria leaves of six feet. 



g. [n the 2274 feet of sandstones, &c. lying above the highest seam of 

 coal, fragments of plants are seen in several of the beds ; they first occur 

 in a bed of sandstone 218 feet from the top, and the plants are converted 

 into coal; they are often called "drift plants," and stated to be "coated 

 with coal." In one bed there are " carbonized drift plants of large dia- 

 meter," say one foot, the stems lying prostrate ; and 1520 feet below this, 

 there is a sandstone " fit for grindstones, with a few Catamites nearly at 

 right angles to the plane of the beds, as if in situ, but forced over at the 

 top;" this sandstone rests on a black carbonaceous shale two feet thick, 

 but it is not stated whether the Calamites are fixed in this carbonnceous 

 stratum. Between this last and the first seam of coal, which is only one 

 inch thick, there are three feet of a " greenish-grey sandstone with Stig- 

 maria Jicoides," succeeded by two feet of *' grey argillaceous shale with im- 

 pressions offei'Tis and other plants." 



Between the seventy-fifth seam, half an inch, and the seventy-sixth, two 

 inches thick, are eighty-four beds of sandstone from a foot to 11/ feet 

 thick, together 1223 feet; and twenty of these beds, all called greenish- 



