They would not thus form a layer of flint keeping more or less to the same level in the chalk. At the periphery, where they entered the area, they would be lower in the chalk, and gradually rise.

The blackest flint nodules I have seen occur in a chalk-pit near Faversham, but the apparently black silica becomes white when powdered, showing it to be merely an optical effect.

Publishing once gave us a well-regarded history of the pencil (Henry Petroski, 1990). There has been a good book devoted to ...

AT one part of Caterham Valley, Surrey, there is an example of an abundance of red flints similar to that mentioned by W. Fream (NATURE, vol. xxv. p. 437). The colour is, doubtless, due to the ...