For example, Physico-Theology contains his recognition of natural variation within species and that he knew that Didelphis virginialis (the Virginia opossum) was the only marsupial in North America.

It also includes one of the earliest theoretical descriptions of a marine chronometer, accompanied by a discussion of the use of vacuum seals to reduce inaccuracies in the operation of timepieces.

His 16-foot-long (4.9 m) telescope (also used when measuring the velocity of sound) was at the top of the tower of St Laurence's Church, where the necessary doors are still in place.

[3] He edited the correspondence and wrote a biography of John Ray, whose 'physico-theology' (natural theology) tradition he continued, making him an early parson-naturalist.

[6] Derham used a telescope from the tower of the church of St Laurence, Upminster, to observe the flash of a distant shotgun being fired, and then measured the time until he heard the gunshot with a half second pendulum.

Measurements were made of gunshots from local landmarks including the Church of St Mary Magdalene, North Ockendon.