As an educator he published Lärobok i geometrien ('Textbook in Geometry'), containing six books of Euclid's Elements and practical applications (3rd edition 1871).

In 1859, a number of members of the growing Baptist movement faced hearings in front of the Bishop's Chapter at the Turku Cathedral.

After Heikel's death in Helsinki in 1867, both his son Viktor (co-founder of the Nya svenska samskolan) and daughter Anna were baptized in Stockholm by the Baptists.

The family received a visit from a Baptist pastor who had been at the hearing with Heikel ten years earlier; they held meetings and his preaching led to more conversions to the movement.

[4][13] This article contains content from the Owl Edition of Nordisk familjebok, a Swedish encyclopedia published between 1904 and 1926, now in the public domain.