During the early years of the Revolution, namely, from 1789 to and including 1791, Lamarck published nothing. Whether this was naturally due to the social convulsions and turmoil which raged around the Jardin des Plantes, or to other causes, is not known. In 1792, however, Lamarck and his friends and colleagues, Bruguière, Olivier, and the Abbé Haüy, founded the _Journal d'Histoire Naturelle_, which contains nineteen botanical articles, two on shells, besides one on physics, by Lamarck. These, with many articles by other men of science, illustrated by plates, indicate that during the years of social unrest and upheaval in Paris, and though France was also engaged in foreign wars, the philosophers preserved in some degree, at least, the traditional calm of their profession, and passed their days and nights in absorption in matters biological and physical. In 1801 appeared his _Système des Animaux sans Vertèbres_, preceded by the opening discourse of his lectures on the lower animals, in which his views on the origin of species were first propounded. During the years 1793-1798, or for a period of six years, he published nothing on zoölogy, and during this time only one paper appeared, in 1798, on the influence of the moon on the earth's atmosphere. But as his memoirs on fire and on sound were published in 1798, it is evident that his leisure hours during this period, when not engaged in museum work and the preparation of his lectures, were devoted to meditations on physical and meteorological subjects, and most probably it was towards the end of this period that he brooded over and conceived his views on organic evolution. It appears that he was led, in the first place, to conchological studies through his warm friendship for a fellow naturalist, and this is one of many proofs of his affectionate, generous nature. The touching story is told by Étienne Geoffroy St. Hilaire.[36]