ANNIVERSARY ADDRESS OE THE PRESIDENT. xlvil 



those which had been called lower Permian in Kansas by Prof. 

 Swallow, are considered by the State surveyors to be a series of 

 strata in no way separable from the great western coal-fields. 



Much uncertainty has prevailed respecting the true value of the 

 coal-measures, which cover more than two-thirds of the surface of 

 the entire State ; and it is by no means dispelled by the information 

 published in the Report ; for without a great additional number of 

 actual trials, it is impossible, in a region where there are so few 

 accidents of stratification to bring the beds to the surface, to predi- 

 cate the continuity or workable character of the seams. Where 

 fuUy developed, in the southern part of the State and even as far 

 north as Fulton and Peoria counties, the measures contain, it 

 is stated, at least five or six workable beds of coal having an 

 aggregate thickness of nearly twenty feet. Dr. D. D. Owen pub- 

 lished a section for Shawneetown, numbering twelve seams, with a 

 total thickness of 35 feet, in 860 feet of strata, included between the 

 base of the so-called Anvil-rock and the top of the conglomerate 

 or Millstone-grit. The lower seams, however, are restricted to the 

 southern j)art of the field, the upper ones only extending to the 

 northern confines, whence it would appear that during the period of 

 the deposition of the coal there must have been a gradual subsidence 

 of the entire surface of the Illinois coal-field. 



Prof. "Worthen ascribes the uneven surface upon which the 

 coal-measures have been deposited, to the thinning out of the strata 

 as they pass northwards, and to the erosion of the valleys down to 

 the subjacent limestones, — those appearances of irregularity which 

 have been exaggerated and explained, by Dr. Stevens, Dr. Norwood, 

 and others, as a division or breaking up into small coal-basins by 

 upheavals and dislocation. 



On the extreme north-eastern border of the coal-field, the mea- 

 sures contain but a single bed of coal, averaging about three feet in 

 thickness, but of unusual importance from its accessibility at mode- 

 rate depth and from its proximity to that great centre of activity, 

 Chicago. An interesting feature exhibited by the sections consists 

 in the frequent repetition of bands of calcareous shale or of limestone 

 abounding in marine fossils, and of which the Director states that 

 " there is probably not one of our principal coal-seams that has not, 

 at some locality in the State, a bed of calcareous shale or a limestone 

 associated with it containing the fossihzed remains of marine ani- 

 mals." The importance of these facts in a review of the dynamics 

 of the formation of the Carboniferous strata, and their parallelism to 

 those of our own Scottish fields, needs not to be enlarged upon. 



Below the coal-measures there occurs a series of " subcarbonife- 

 rous " limestones divided into several groups, known by local names, 

 and which, whilst they have an aggregate thickness of 1500 feet in 

 the southern portion of the State, thin out on the north and dis- 

 appear entirely on the western borders of the coal-field. At the 

 base of the division called the Burlington limestone, well known to 

 palaeontologists for the beauty and variety of the Crinoidea occurring 

 at its northern outcrop, follows a series of beds, chiefly gritstones 



