In 1736 Bayes wrote a tract on Newton's fluxions. The tract was one of several explanations of fluxions which appeared following Berkeley's attack upon Newton's ideas in The Analyst. Bayes began with a careful discussion of the meaning of fluxions and prime and ultimate ratios. He proceeded to develop the properties of prime and ultimate ratios in a way not unlike Cauchy's treatment of limits, using these results to prove some basic theorems concerning the calculation of fluxions. © 1980, All rights reserved.
Smith, G. C. (1980). Thomas Bayes and fluxions. Historia Mathematica, 7(4), 379–388. https://doi.org/10.1016/0315-0860(80)90002-6