The present work needs but little introduction to the English public. The author, M. F. Marion, who holds a high official scientific position in Paris, is well known, especially in Europe, as a popular writer on the "Wonders of Optics," and kindred subjects. As a rule, the original text has been strictly adhered to by the Translator, but in a few instances certain anecdotes of a local character have been altered so as to be more generally applicable, or condensed to make room for the chapter on the Spectroscope, which is entirely original.