6. “Bunsen Burner.” In this burner, at the lower end of the hollow stem through which the gas passes, there is a lateral orifice which admits the air necessary for combustion. This orifice can be made larger or smaller by means of a diaphragm which is used as a regulator. If a moderate amount of air enters, the gas burns with a luminous flame, but if a strong and steady current is admitted, the carbon is rapidly oxidized, the flame loses its brightness, and burns with a pale blue light, scarcely perceptible, and with intense heat. 7. “Voltaic Arc.” A most beautiful effect, obtained from the electric light. At the terminals of a battery, pieces of charcoal are connected and placed in contact until the current causes them to become incandescent. Then they are separated about the tenth of an inch, and it is found that a luminous, exceedingly brilliant arc connects the two points. 8. “Hell Gate.” The name of a narrow channel between Long Island and Manhattan Island. Until recently the numerous reefs made it impassable for large ships and dangerous for small ones. In 1851 the first efforts were made to open the channel, by submarine blasting. In 1876, after many vain attempts, the work was carried to a successful issue. The total amount of money expended by Congress for this work since 1868 was $1,940,000. 9. “Æolus.” A descendant of the founder of the Æolian race. He became the ruler of certain islands in the Tyrrhenian Sea, which from him were called the Æolian Islands. He is said to have taught his subjects to use sails on their ships, and to have foretold the nature of the winds that were to rise. Homer said of him that Jupiter had given him rule over the winds. This led to his being regarded as the god of the winds, which he was supposed to keep shut up in a mountain. TALK ABOUT BOOKS. It would be difficult for a biography of Sydney Smith, that man who always took short views of life, hoped for the best, and put his trust in God, to be other than interesting. Mr. Reid’s biography[L] is so interesting that the reader quite forgets to criticise. It is a many-sided sketch of the brave hearted dominie. It tells his history, to be sure, but one gets a very good idea of many of his associates as well; it tells his route through life, and as a happy idea adds descriptions and illustrations of the various localities in which he lived, as they are to-day. There is just enough quotation from the reverend Sydney to give pith to the sober, clear narrative of the writer, and just enough of the “Times” to keep one in sympathy with his age. Several letters and essays never before printed appear in the volume. Mr. Reid, we are pleased to see, presents the courage, the unfailing hope, and the abundant common sense of his subject as characteristics of more importance than his wit.