John Irving, WS

Lord Eldin's younger brother, William Clerk, was the trusted friend and comrade of young Walter Scott . And it may be observed here, by the way, that the friend of both, John Irving, was half-brother to Mrs. Clerk, John Clerk Maxwell's mother.

Source: The life of James Clerk Maxwell:with a selection from his correspondence and occasional writings and a sketch of his contributions to science (Google eBook) By Lewis Campbell, William Garnett Macmillan, 1882

From p. 16..

http://books.google.com/books?id=d2oOAAAAIAAJ&source=gbs_navlinks_s

Other References

• The Society of Writers to Her Majesty's Signet; 1890; page 109