I have no idea if the article below is the same HENRY DERRY that is the father of your THOMAS DERRY -- but thought I would take a chance and share it with you anyway.
I found this interesting article from a book called "THE MYSTERIES OF ONTARIO" (page 208) by John Robert Columbo for anyone who might be interested. (This is not my line).
STRATFORD Derry's Head
The body of a middle-aged labourer named HENRY DERRY was found in a pine coffin which was floating on the Avon River not far from the park behind the Board of Education building, on November 1876. The body was headless. After the inquest, a medical student confessed to removing the body from the Catholic cemetery and the head from the body to further his studies in anatomy. Thereafter, the Avon River was said to be haunted by the headless ghost of HENRY DERRY. A skull was found in the vicinity in 1980, and according to forensic scientists, it was probably DERRY's. (289, 354)
I did a brief search for a HENRY DERRY in Ontario and found a death record on Ancestry.com that said HENRY DERRY died on 29 April 1876 in Perth. He was estimated to be born about 1839 in Ireland. The actual death record can be viewed which stated that HENRY died in gaol of pleurisy, that he was a cooper and was 37 years old.