William Berwick wrote only 13 papers and a monograph. Ill health prevented him from undertaking more extensive work.
Berwick was an algebraist who worked on the problem of computing an integral basis for the algebraic integers in a simple algebraic extension of the rationals. He also studied ideals in the ring of algebraic integers. His book Integral Bases published in 1927 is a significant contribution.
The existence of such a basis can be easily proved but practical methods to compute such a basis are much harder. The heavy numerical computationals involved in Berwick's work kept it outside the mainstream of algebraic number theory.
Berwick also gave, in 1915, necessary and sufficient conditions
for a quintic equation to be soluble by radicals.