C. G. Boone.
Answer.—A night glass is simply a small terrestrial telescope, or spy-glass, ordinarily in the form of a large opera-glass, with an unusually large lens in the end toward the object to be viewed, called the object-glass, which serves to concentrate a large amount of light, and so render objects seen at night much more distinct than when viewed by either the naked eye or an ordinary spy-glass. Since it is a principle in optics that “it is impossible, by any optical arrangement whatever, to obtain an image whose brightest part shall surpass the brightest part of the object,” it is obvious that nothing seen through a night-glass, even in the clearest night, can appear as distinct as in daylight.
AMERICAN HISTORIANS.
Wanda, Ill.
Will you please publish a list of the principal American historians?
S.
Answer.—Assuming that by “American historians” you mean historians born in America, we give the following list, naming first those who wrote chiefly of our own country, and afterward those who have written mainly of other countries: J. S. C. Abbott, b. 1805; d. 1877; George Bancroft, 1800; Richard Hildreth, 1807-1865; C. E. A. Gayarre, 1805; Francis Parkman, 1823; John C. Ridpath, 1840; John D. G. Shea, 1824; Jared Sparks, 1789-1866; James F. Cooper, 1789-1851; Hubert H. Bancroft, and Thomas H. Burton. W. H. Prescott, 1796-1859; John Lathrop Motley, 1814-1877, and Royal Robbins, 1788-1861.
SANDPAPER.