St. John's Chapel in the Tower of London are fine examples of Norman
work.

The castles consisted of a square keep, or citadel, with walls of
immense thickness, having a few slitlike windows in the lower story
and somewhat larger ones above. In these buildings everything was
made subordinate to strength and security. They were surrounded by a
high stone wall and deep ditch, generally filled with water. The
entrance to them was over a drawbridge through an archway protected by
an iron grating, or portcullis, which could be raised and lowered at
pleasure. The Tower of London, Rochester Castle, Norwich Castle,
Castle Rising, Richmond Castle, Carisbrooke Keep, New Castle on the
Tyne, and Tintagel Hold were built by William or his Norman
successors.

The so-called Jews' houses at Lincoln and St. Edmundsbury are rare and
excellent examples of Norman domestic architecture. Although in many
cases the Norman castles are in ruins, yet these ruins bid fair to
stand as long as the Pyramids. They were mostly the work of
churchmen, who were the best architects of the day, and knew how to
plan a fortress as well as to build a minster.

V. General Industry and Commerce

157. Trade.

No very marked change took place in respect to agriculture or trade
during the Norman period. Jews are mentioned in a few cases in Saxon
records, but they apparently did not enter England in any number until
after William the Conqueror's accession. They soon got control of