Brick-and-chalk Vaulting at the Deanery Garden, Sonning
Block Chalk
BLOCK CHALK
“Chalk” is a term somewhat loosely used to denote the soft white limestone—the “Creta Scriptoria”—that is cousin to Marl on one side and to Ragstone on the other.
In its purest form chalk consists of over 95 per cent. of carbonate of lime in the form of fine granular particles held together by a calcareous cement, its organic origin being clearly traced in the remains of the minute sea creatures with which it abounds.
Hewn blocks of chalk have been used for walling and vaulting from immemorial times, and, where not exposed to direct erosion by the weather, remain to this day as clean-cut as when they were first quarried and a very great deal harder.
The filling in of the great vaults at Salisbury Cathedral and in the Bishop’s Palace are of chalk, whilst innumerable lesser buildings of more or less antiquity still remain to us as monuments to the excellence and durability of this stone.
Chalk, too, was often used in combination with flint or brick to build the engaging chequer-work walls that embellish so many downland villages.
At Medmenham there are cottages both old and new of hewn rock chalk, and both the Berks and Bucks banks of the Thames have many buildings to show of this beautiful material.