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To the Editor.
—The author, Chevallier, was not a physician but a civil engineer. He seems to have known quite a bit about optics but was mostly interested in the practical side of his craft. In those days glasses were not prescribed by physicians, and he was probably the first reputable and learned optician to practice in Paris. He always had an eye to commerce and often blew his own horn, a characteristic which may be justified when one compares him with his colleagues of that day.The second half of the book is of no great interest to ophthalmologists. It gives a description of various optical instruments, such as telescopes, mirrors and microscopes. The first half deals with the eye and with glasses. There is nothing one can learn today in these two hundred pages; but, as is often the case in old books, one finds amusing things—and now