1818.] M. Senebier. 243 



of a disposition and turn of mind very congenial to his own. 

 Nearly at the same time he was appointed pastor in the parish of 

 Chancy, about nine miles from Geneva, which is described " as 

 a delicious rural retreat, where every thing was in harmony with 

 the state of his heart." In this situation he spent four of the 

 most pleasant and useful years of his life, until in 1773 he quit- 

 ted his rustic abode, and succeeded M. Lullin as the public 

 librarian of Geneva. Soon after his appointment he undertook 

 the task, in conjunction with M. Diodati, of forming a catalogue 

 of the library, arranged according to the order of the subjects, 

 a task which was completed in three years. About the same 

 period he entered upon the study of chemistry, as a pupil of 

 Prof. Tingiy, and soon began to exercise his pen in discussing 

 the merits of the doctrine of phlogiston, which was then becom- 

 ing the great topic of controversy. It was also at this time that 

 he undertook, at the request of his friend Bonnet, the transla- 

 tion of Spallanzani's " Opuscules de Physique vegetale et 

 animale." 



In the year 1779 M. Senebier published his first memoirs on 

 the influence of light, a subject in which he afterwards laboured 

 with much attention, and is the topic on which he may be 

 considered as having made the most important additions to our 

 knowledge. His experimental career was stopped for some 

 time by a severe illness, occasioned, as we are informed, by the 

 grief which he experienced in consequence of the death of his 

 father; but he embraced the first moments of his convalescence 

 to resume his labours, when he particularly directed his attention 

 to the green matter which is often formed in water exposed to 

 the action of light. This had been conceived by some natural- 

 ists to be of animal origin ; but Senebier clearly proved its 

 vegetable nature, and determined it to be a conferva, affording 

 a shelter or nidus for numerous insects, but in no way partaking 

 of their properties. He resumed his researches into the action 

 of light upon vegetables in the year 1782, and directly opposed 

 the opinion that had been advanced by Ingenhousz, who con- 

 ceived the action of leaves upon the air during the night to be 

 deleterious. Probably in this instance neither of the opinions 

 that were maintained are correct ; but in the course of the 

 discussion to which the controversy gave rise, Senebier made a 

 series of important observations, which tended considerably to 

 enlarge our knowledge on the subject of vegetation and the 

 chemical change which this function produces on the air. There 

 is so much uncertainty in the results of experiments on living 

 vegetables, that after all the researches that have been made, 

 there are comparatively but few points that can be considered 

 as absolutely proved ; but among these we may probably rank 

 one of Senebier's discoveries, that when the leaves of plants are 

 acted upon by the sun's rays, they absorb carbonic acid, decom- 

 pose it, retain the carbon, and discharge the oxygen. 



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