412 Miscellaneous. [April, 



Further remarks on the Ball Coal of the Burdwan mines. By Henry 

 Piddington, Curator Museum of Economic Geology. 



Mr. Homfray having at my request furnished us with a block of the coal 

 from the seams of which the ball coal is taken, I have examined it very carefully 

 and the following are my results. 



Description. 



The block of coal averages about 10 inches by 9, and is somewhat more than 

 6 inches thick, so that it may be, in round numbers, about the third of a cubic 

 foot. 



At the top and bottom of the seam the block has the usual soft, velvet-like 

 coating of carbonaceous matter, with traces of fossil plants, so frequently found 

 upon the seam sides of coal of all kinds, and in which impressions, more or less 

 distinct, of vegetable forms are usually seen. The cross fracture however is 

 difficult to describe. It is on one face tolerably vertical and perpendicular to 

 the planes of the upper and under surfaces, like a block of English coal, but in the 

 direction of the layers of alternate bright and dull coal of which it is composed, 

 it is wavy, though not very deeply so. But upon the other three faces its struc- 

 ture and fracture can only be described by calling it a sort of flattened, globular 

 concretionary one, having much the appearance of many softened globula, 

 masses of coal pressed into flattened layers amongst layers of common coal, and 

 where a lump is detached it assumes an irregularly elongated form, globular or 

 bulging at the ends and sides, and flat above and below ; appearing as if, when 

 free from pressure, it had been of the rounded form of the balls of coal, and 

 yet (and it is this which constitutes the difficulty of imagining any hypothesis to 

 account for this kind of structure), the horizontal layers of dull and bright glance 

 coal run through the globular and conchoidal projections and hollows of the com- 

 pressed balls, as regularly as through the simply stratified or foliated parts. 

 The only thing indeed one can liken it to geologically, would be a mass of 

 gneiss just decomposing and separating into irregularly shaped globular or ovoidal 

 concretions, as granite does into spherical ones, but preserving its stratification,* 

 We have one concretion detached from the mass about 4 ins. by 1\ and \\ 

 thick which is very distinctly a flattened and elongated ball, and it has left a 

 hollow mould in the large mass where imbedded, yet it is distinctly formed of 



* Boase (Primary Geology, p. 114,) describes various kinds of conglomerated rock- 

 and of mica amongst others, but the nuclei of his instances are all different from the envel- 

 oping mass, but our balls are perfectly identical with it ! 



