Α α Alpha a Β β Beta b Γ γ Gamma g Δ δ Delta d Ε ε or ϵ Epsilon ĕ Ζ ζ Zeta z Η η Eta ē Θ ϑ or θ Theta th Ι ι Iota i Κ κ Kappa k Λ λ Lambda l Μ μ Mu m Ν ν Nu n Ξ ξ Xi x Ο ο Omicron ŏ Π π Pi p Ρ ρ Rho r Σ σ or ς Sigma s Τ τ Tau t Υ υ Upsilon u Φ φ Phi ph Χ χ Chi ch Ψ ψ Psi ps Ω ω Omega ō POPULAR LITERATURE OF ASTRONOMY The following brief bibliography, while making no pretense at completeness, may serve as a useful guide to supplementary reading: _General Treatises_ YOUNG. _General Astronomy._ An admirable general survey of the entire field. NEWCOMB. _Popular Astronomy._ The second edition of a German translation of this work by Engelmann and Vogel is especially valuable. BALL. _Story of the Heavens._ Somewhat easier reading than either of the preceding. CHAMBERS. _Descriptive Astronomy._ An elaborate but elementary work in three volumes. LANGLEY. _The New Astronomy._ Treats mainly of the physical condition of the celestial bodies. PROCTOR and RANYARD. _Old and New Astronomy._ _Special Treatises_ PROCTOR. _The Moon._ A general treatment of the subject. NASMYTH and CARPENTER. _The Moon._ An admirably illustrated but expensive work dealing mainly with the topography and physical conditions of the moon. There is a cheaper and very good edition in German. YOUNG. _The Sun._ International Scientific Series. The most recent and authoritative treatise on this subject. PROCTOR. _Other Worlds than Ours._ An account of planets, comets, etc. NEWTON. _Meteor._ Encyclopædia Britannica. AIRY. _Gravitation._ A non-mathematical exposition of the laws of planetary motion. STOKES. _On Light as a Means of Investigation._ Burnett Lectures. II. The basis of spectrum analysis. SCHELLEN. _Spectrum Analysis._ THOMSON (Sir W., Lord KELVIN), _Popular Lectures, etc._ Lectures on the Tides, The Sun's Heat, etc. BALL. _Time and Tide._ An exposition of the researches of G. H. Darwin upon tidal friction. GORE. _The Visible Universe._ Deals with a class of problems inadequately treated in most popular astronomies. DARWIN. _The Tides._ An admirable elementary exposition. CLERKE. _The System of the Stars._ Stellar astronomy. NEWCOMB. Chapters on the Stars, in _Popular Science Monthly_ for 1900. CLERKE. _History of Astronomy during the Nineteenth Century._ An admirable work.