and others once dear to him, had found their last resting-place in it.
For his support he had to rely on the lenses which he made—an art which he had mastered during the years immediately preceding his exile. He made lenses for spectacles, microscopes, and telescopes, and his friends sold them for him. The work suited his tastes well enough, be cause it kept him in touch with his scientific studies. And he evidently excelled in it, for later on his fame as an optician attracted the notice of Huygens and Leibniz, among others. But it was an unfortunate occupation otherwise. The fine glass-dust which he inhaled during his work must have been very injurious to his health, especially when we bear in mind that he eventually died of consumption, and that he probably inherited the disease from his mother, who died so young. For the time being, however, it was a congenial occupation, and, with his frugal habits, left him sufficient time to pursue his scientific and philosophic studies.
As already suggested, Spinoza did not stay long in Ouwerkerk, but returned, after a few months, to Amsterdam, where he remained till 1660. Of the events which happened during this period (1656-1660) we possess the most meagre information. Apparently he gave some private lessons in philosophy, and pursued his studies unremittingly. At the end of this period he had already left Descartes behind him, and had thought out the essentials of his own philosophy.
From Spinoza's subsequent correspondence, we obtain a glimpse of his friends and associates during this period, while the opening pages of his Improvement of the Understanding at once enlighten and mystify us about his life during those last years in Amsterdam.
After leaving Amsterdam in 1660 Spinoza continued a friendly correspondence with several residents in Amsterdam, whom he also visited for a short time in 1663. These
