VINE: NOTES ON FOSSIL POLYZOA. 
393 
of the lower members." And in the same letter he dkected my 
attention to the rotten Permian material found in the quarry near 
Hampole : a locality mentioned in his paper on the South Yorkshire 
Permians. Will students living- near these localities kindly search 
the shales and Rotten Permian Limestone for me, as mine is largely 
home, and very little out work ? 
ON THE COMPOSITION OF THE ''COAL BALLS" AND "BAUM POTS" 
IN THE LOWER COAL MEASURES. BY H. B. STOCKS. 
In the Halifax Hard Bed Coal seam it is well-known that nodules 
occur in abundance ; these nodules are locally known as " coal balls." 
Just above the coal is a bed of shale in which nodules called " baum 
pots " are found ; the latter is divided from the coal by a thin shale 
containing- Aviculopectens in abundance ; under the coal is a hard 
fire-clay called ganister. 
"Coal balls " are generally spherical, of a brown or greyish- 
brown colour internally, they are very hard and contain the remains 
of plants, in some instances being largely composed of wood fossihzed 
by carbonate of lime ; they have generally a coating of iron pyrites, 
which occasionally replaces the carbonate of lime and becomes the 
chief constituent of the ball. 
"Baum pots" may be divided into two kinds — first, those 
consisting of successive coatings of mineral matter surrounding a 
central portion ; second, those showing stratification like the shale 
in which they occur. " Baum pots " are generally oval, of a grey 
colour, hard and compact and often contain fossil shells. They have 
frequentl}^ an outer coating of iron pyrites. 
I am not aware that the composition of these nodules has been 
examined in detail, it being generally stated that they are composed 
of limestone coated with iron pyrites. VVith a view to learn some- 
thing more as to their composition I have made analyses of two 
*'coal balls" and one "baum pot" from the Halifax district. On 
