POT-STONES OF HORSTEAD. 
291 
izontal layers of small flints. I visited in the year 1825 an 
extensive range of quarries then open on the river Bure, near 
Horstead, about six miles from Norwich, which afibrded a 
continuous section, a quarter of a mile in length, of white 
chalk, exposed to the depth of about twenty-six feet, and 
covered by a bed of gravel. The pot-stones, many of them 
pear-shaped, were usually about three feet in height and one 
foot in their transverse diameter, placed in vertical rows, 
like pillars, at irregular distances from each other, but usu¬ 
ally from twenty to thirty feet apart, though sometimes 
Fig. 23T. 
From a drawing by Mrs. Gunn. V 
View of a chalk-pit at Horstead, near Norwich, showing the position of the 
pot-stones. 
nearer together, as in the above sketch. These rows divl 
not terminate downward in any instance which I could ex¬ 
amine, nor upward, except at the point where they were cut 
ofl* abruptly by the bed of gravel. On breaking open the 
pot-stones, I found an internal cylindrical nucleus of pure 
chalk, much harder than the ordinary surrounding chalk, 
and not crumbling to pieces like it, when exposed to the 
winter’s frost. At the distance of half a mile, the vertical 
piles of pot-stones were much farther apart from each other. 
Dr. Buckland has described very similar phenomena as char¬ 
acterizing the white chalk on the north coast of Antrim, in 
Irelaiid."^ 
Vitreous Sponges of the Chalk.—These pear-shaped masses 
of flint often resemble in shape and size the large sponges 
* Geol. Trans., 1st Series, vol. iv., p. 413. 
