50 REPORT — 1842. 



Pecten, Goniatites, Posidonia, and other shells of marine origin. The total thick- 

 ness of the deposits varies in different parts of the field; in a line from Manchester, 

 through Ashton, to the limestone shales of Hollins Brook, the thickness is about 

 2000 yards; and there are 75 beds of coal exceeding one foot in thickness, forming 

 altogether 150 feet. In a line throngh Worsley, Bury, Burnley, &c, to the lime- 

 stone shales of Pendlehill, there are 36 seams, only ten of which are less than one 

 foot in thickness, amounting to 93 feet of coal ; in these sections the smaller seams 

 are not taken into account. The author states that the variable character of these 

 coal seams and the accompanying strata, make it difficult to lay them down upon a 

 map ; the lower seams can be classed by the gritstone rocks which contain them, as 

 shown by Mr. Elias Hall, but the middle and upper seams divide and thin out in 

 such a manner as to render their identification very difficult. He then proceeds to 

 describe the roofs, or strata immediately overlying the coal seams, the coal itself, and 

 the floors or strata immediately underlying the beds of coal. 



I. Roofs. — The deposits forming the roofs vary at different places, even over the 

 same seam. There are four kinds of roofs : — 1. A fine mixture of alumina and silica, 

 with oxide of iron, and a trace of the carbonates of iron and lime ; these are generally 

 known as blue binds, and are of most frequent occurrence ; they almost always con- 

 tain ferns, and remains of Stigmaria, Sigillaria, Ulodendron and Lepidodendron, and 

 beds of the Unio and other shells. The Sigillariae, &c. are often found standing 

 erect at right angles to the planes of stratification ; these instances chiefly occur in 

 the middle field, at Pendleton, Dixon-fold, Wigan, &c. Sometimes they are found 

 with their roots running into and resting on the seams, and more frequently the hole 

 of the tree rests on the coal itself, without exhibiting any trace of roots. The Sigil- 

 lariae are by far the most common ; at Pendleton and Dixon-fold they occur as abun- 

 dantly as they could possibly have grown : the author had observed three specimens 

 at Pendleton, 24 feet high and about 3 feet in circumference, standing in a shaft 11 

 feet in diameter. 2. Roofs of sandstone are not common, and where they do occur 

 the coal is generally inferior in quality; the fossils found in the sandstone are usually 

 prostrate coal plants, Stigmaria;, Sec. 3. Black shale roofs are frequent, and cover 

 most of the best house-fire and caking coal; they seldom contain plants, though, in 

 a few instances, upright Sigillarias have been found. Bivalve shells, detached scales 

 and teeth of fish frequently occur in them, and with the Microeonchus carbonarius 

 and casts of Cyprides sometimes constitute nearly the entire mass; almost all the 

 black shale roofs of the lower field teem with remains of Pecten, Goniatites, Posi- 

 donia, and remains of fishes. 4. Shales ivith highly bituminous schists, forming roofs, 

 are not of frequent occurrence; they are found at Peel and Pendleton, and contain 

 abundant remains of fish, mostly entire. At Bradford and at Ardwick, in the roof of 

 the thin coat intercalated with the limestones, the detached teeth, bones and scales of 

 fish occur, mingled with countless myriads of the remains of Cypris and Microeonchus. 



II, Coal and Cannel Seams. — The author describes two varieties of coal, the cubical 

 where the cross cleavage runs at right angles to the main cleavage, and the rhom- 

 boidal where it makes an acute angle; the first form generally occurs in the upper 

 and lower portions of the field, the latter orevails in the middle. The main cleavage, 

 he observes, is in most cases parallel witfi the principal fault in the vicinity. The 

 beds of cannel are generally found on the top of the coal, and nearly always contain 

 remains of fishes, often bivalve shells, but hitherto have exhibited no trace of Micro- 

 eonchus, and rarely any leaves or stems of plants, whilst the upper portion of coal 

 seams frequently exhibit traces of Sigillarias, Lepidodendra, Calamites, &c. In the 

 six-feet seam at the new pit of the Pendleton Company, several rounded stones of 

 fine siliceous grit were found, but as they occurred near the great fault of 1 000 yards, 

 they might have fallen in during the dislocation. The coal seams are either simple, 

 and continue undivided over large tracts of country, or split and divide into several 

 distinct seams ; the former generally occur in the lower portion of the field, the lat- 

 ter in the middle and upper part. It is owing to this tendency to divide, that the 

 thick seams of Clifton and Radcliffe cannot be well identified with the thinner and 

 more numerous seams of Oldham, Ashton and Bradbury; in the four-feet mine at 

 Pendleton the author has observed that the coal on the N.W. forms one undivided 

 seam of 5 feet in thickness, but that towards the S.W. a thin bed of fireclay full of 

 Stigmaria; appears in it; and in Mr. Fitzgerald's pit to the S.E. it gradually thickens 

 until at a distance of 900 yards from the point first observed, it has increased to 3 



