The Vault of Heaven. By Richard A. Gregory. (Methuen.)— This
"Elementary Text-Book of Modern Physical Astronomy" is one of the "University Extension Series." The larger part of the volume is naturally devoted to a description of the Solar system. Chap. vi. treats of "Comets and Shooting-Stars ; " shooting-stars belong wholly to our system ; of comets, some do, as Encke's, which has an orbit within that of the planet
Jupiter ; some are visitors from outside space, either periodical, or coming once only. After this, we have a chapter entitled " In Boundless Space ; " here the account of the varying stars is specially noticeable. The "Chemistry of the Stars and Nebulte." with an account of the spectroscope, supplies the subject of another chapter. Finally, we have an account of that pro- foundly interesting art, "Celestial Photography," the achieve- ments of which are probably still only in their beginning.
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