[1][2] He was born in Jamaica where his father, William Garland Barrett, who was an amateur naturalist, Congregationalist minister and a member of the London Missionary Society, ran a station for saving African slaves.

The family returned to their native England in Royston, Hertfordshire in 1848 where another sister, the social reformer Rosa Mary Barrett was born.

Barrett discovered Stalloy (see Permalloy), a silicon-iron alloy used in electrical engineering and also did a lot of work on sensitive flames and their uses in acoustic demonstrations.

[4] When Barrett developed cataracts in his later years, he also began to study biology with a series of experiments designed to locate and successfully analyze causative agents within the eyes.

[4] From 1908–14 Barrett was active in the Dublin Section of the Society for Psychical Research, a group which attracted many important members including Sir John Pentland Mahaffy, T.W.

[10] Barrett helped to publish Frederick Bligh Bond's book Gate of Remembrance (1918) which was based on alleged psychical excavations at Glastonbury Abbey.

[15][16] Barrett has drawn criticism from researchers and skeptics as being overly credulous for endorsing spiritualist mediums and not detecting trickery that occurred in the séance room.

[17] Skeptic Edward Clodd criticized Barrett as being an incompetent researcher to detect fraud and claimed his spiritualist beliefs were based on magical thinking and primitive superstition.

[18] Another skeptic Joseph McCabe wrote that Barrett "talks nonsense of which he ought to be ashamed" as he had poor understanding of conjuring tricks and failed to detect the fraud of the medium Kathleen Goligher.