Around 1865 John Thomas Blight (age 29) had a mental breakdown and was incarcerated for the remainder of his life in Bodmin Mental Asylum.

Nænia Cornubiæ by William Borlase Introductory Preface. To the labours of Mr. J. T. Blight, F.S.A., he owes a considerable debt of gratitude; nor must he forget to bear testimony to the excellent manner in which his brother, Mr. Joseph Blight, has carried out the important share of the work (viz., the wood engravings,) allotted to him.

Ancient Crosses and Other Antquities in the West of Cornwall. Ancient Crosses and Other Antquities in the West of Cornwall Drawn and Engraved by J. T. Blight. 1856.