The Jesuits made important contributions to the development of science, including meteorology, particularly by establishing observatories in various countries during the 19th century including Jersey. However, over the years the contribution of the observatories and the highly intelligent and dedicated scientists who worked in them have been neglected and largely forgotten. This work aims to put the principles of the Jesuit order into scientific context, then outlines the career and contribution to meteorology of one individual in particular, Père Marc Dechevrens. He arrived at the Zi-ka-weï Observatory in Shanghai, China in 1873 and was its Director from 1875 until 1887. Later he came to Jersey where he was Director of the Maison St. Louis Observatory for the 30 years from 1894 until 1923. This work is a revised and much expanded version of an unpublished paper written in 2005.