"[L]e principal fondement du calcul différentiel". According to François-Joseph Fétis, (Biographie universelle…, p. PA194, at Google Books, vol. 8, p. 194), the statement "the main foundation of differential calculus abstracted from any consideration of infinitely smalls and limits" was first printed in the Journal de l'École polytechnique, vol. 9, p. 5.