Speidell was a mathematics teacher in London[1][2] and one of the early followers of the work John Napier had previously done on natural logarithms.
[4][5] He then diverged from Napier's methods in order to ensure all of the logarithms were positive.
[7] Along with William Oughtred and Richard Norwood, Speidell helped push toward the abbreviations of trigonometric functions.
[7] Speidel published a number of work about mathematics, including An Arithmeticall Extraction in 1628.
[8] His son, Euclid Speidell, also published mathematics texts.