TF. S. Gresley — A Coal Pebble in a Coal-seam. 159 



Description of the Pebble. 

 Fairly well-rounded, but bearing decided traces of vertical joints 

 belonging to the layer or bed from which it was doubtless derived. 

 In form flattish subangular, being rather suggestive of a flattened 

 pear. The grain or laminae of the material lie parallel with the 

 flatter sides. Thickness about il inch, but quite uneven ; not 

 unlikely the thickness of the pebble approximates that of the 

 individual band from which it was derived. Longer diameter 

 3^ inches ; maximum width about 2 inches. The surface all over 

 may be described as rough and uneven, considerably pitted, and 

 quite concave on part of one of its vertical sides, the rest being 

 very convex. The roughness of surface is about similar to that of 

 a Brazil nut. The pittings, etc., upon the horizontal or flatter 

 parallel surfaces are mainly due to the wearing away of little patches 

 of fossil charcoal. A few shallow and parallel stria3 run approximately 

 parallel with the longest diameter, and occur mainly on one flat side 

 only. They are just such scratches that a fragment of coarsish 

 sandstone makes when rubbed across similar coal. The material 

 is very hard, compact, dull, heavy coal, and contains, besides 

 numerous wee specks, streaks or shred-like bits of lustrous hydro- 

 carbonaceous materials, very many macrospores or spore cases 

 measuring about -57,- inch across. These fossils show up quite con- 

 spicuously on the pebble's surface.' In short, the coal is not at all 

 unlike that of some of the spirey layers belonging to the ' Main Coal ' 

 seam of the same field, nor of similar hard layers found in the ' Koaster ' 

 coal some 10 miles to the east, and in the ' Slate ' seam near Nuneaton, 

 in Warwickshii'e, 15 miles distant. It is extremely probable that the 

 matrix of this pebble consists mainly of spores, because Mr. Edward 

 Wethered, F.G.S., found that a micro-slide of coal, to all appearance, 

 so far as the author can see, resembling this, was so composed. The 

 pebble weighs about 2\ oz. 



History of the Pebble. 

 From its position in the coal-seam the best explanation is that it got 

 there by flotation, in all probability was dropped from the roots of 

 a tree, in which it had become entangled in some way, floating in 

 water over the site. Thus the inference is that this seam of coal was 

 deposited below water. The pebble, to become such as described, has 

 presumably travelled a considerable distance — has, at all events, been 

 swirled about in water, and by attrition and pressure with rock debris 

 become worn down to its present shape and size. Now, such subjection 

 to rough treatment must of course have taken place before it got into 

 the soil, or, say, pebbly deposit, in which the tree-ferns, etc., would seem 

 to have grown. This ' soil ', in part at any rate, was formed of Coal- 

 measure debris, so that Coal-measures actually containing perfectly 

 formed coal must have been elevated and undergoing denudation at 

 this very time, i.e. shortly before the forming of the Little Coal seam. 

 Granting this, it is evident that the coal-bed containing the spirey 

 layer of which our pebble is a part was an older seam than the Little 

 Coal. There is no evidence that I know of in the present coalfield that 



1 The pebble takes a high polish sinailar to sinrey coal. 



