Cassegrain: un c?l?bre inconnu de l'astronomie instrumentale Cassegrain: a famous unknown of instrumental astronomy

Abstract:

Alors qu'au XVII?me si?cle, la r?volution scientifique marque l'?poque et que les ?rudits ne cessent de communiquer leurs d?couvertes dans leurs ouvrages imprim?s ou leurs correspondances, alors que dans ce monde restreint mais non ferm?, tout le monde conna?t tout le monde, un homme de Chartres nomm? Cassegrain reste parfaitement myst?rieux au point qu'on ignorait jusqu'ici tout de lui, y compris son pr?nom! Apr?s avoir rappel? la chronologie des faits qui entourent la publication concernant le `T?lescope Cassegrain' dans le Journal des S?avans en 1672, les auteurs font le point sur l'?tat de l'art du moment, et montrent ce que la science des `miroirs ? voir de loin et ? grossir les esp?ces' doit plus particuli?rement aux quatre grands noms qui y sont associ?s: Mersenne, Gregory, Newton et Cassegrain. Ils analysent ensuite les raisons de la notori?t? de Cassegrain, avant de s'attaquer au probl?me de savoir qui ?tait ce personnage. Gr?ce aux r?sultats d'une enqu?te longue et m?ticuleuse consacr?e ? la recherche de manuscrits in?dits et au d?pouillement sur place des registres paroissiaux des lieux o? il a v?cu, Chartres tout d'abord, Chaudon, pr?s de Nogent-le-Roi ensuite, l'homme est d?sormais clairement identifi?, et quelques indications sur sa personnalit? se font enfin jour. Il s'agit de Laurent Cassegrain, n? dans la r?gion de Chartres vers 1629, et mort ? Chaudon (Eure-et-Loir) le 31 ao?t 1693.

Although the scientific revolution dominates the 17th century and scholars are ceaselessly communicating their discoveries in their printed works or their correspondence, although in this restricted but not enclosed world everybody knows everybody else, nevertheless a man from Chartres (France) named Cassegrain remains so completely mysterious that absolutely nothing was known about him until now, not even his Christian name! After an account of the chronology of the events accompanying the publication concerning the `Cassegrain reflecting telescope' in the `Journal des S?avans' in 1672, the state of the art at that time is reviewed and it is shown how the science of `the mirrors to see far and to magnify objects' is particularly indebted to the four great names which are associated with it: Mersenne, Gregory, Newton and Cassegrain. The reasons for Cassegrain's fame are analysed before the formidable task of finding out who he was is undertaken. Following long and meticulous investigations devoted to the search for unpublished manuscripts and the analysis of the parish registers in the places where Cassegrain lived (Chartres first and then Chaudon, near Nogent-le-Roi) the man is henceforth clearly identified and some details about his life and personality are at last brought to light. He is Laurent Cassegrain, born in the region of Chartres around 1629, who died at Chaudon (Eure-et-Loir) on the 31 August 1693.