_Our Native Songsters._ By Anne Pratt, Author of "Wild Flowers." With 72 coloured plates. 16mo. _Cloth boards_ 6 0 _Selborne (The Natural History of)._ By the Rev. Gilbert White. With Frontispiece, Map, and 50 woodcuts. Post 8vo. _Cloth boards_ 2 6 _Toilers in the Sea._ By M. C. Cooke, M.A., LL.D. Post 8vo. With numerous illustrations. _Cloth boards_ 5 0 _Wayside Sketches._ By F. Edward Hulme, F.L.S., F.S.A. With numerous illustrations. Crown 8vo. _Cloth boards_ 5 0 _Where to find Ferns._ By Francis G. Heath, Author of "The Fern Portfolio," &c. With numerous illustrations. Fcap. 8vo. _Cloth boards_ 1 6 _Wild Flowers._ By Anne Pratt, Author of "Our Native Songsters," &c. With 192 coloured plates. In two volumes. 16mo. _Cloth boards_ 12 0 LONDON: Northumberland Avenue, Charing Cross, W.C.; 43, Queen Victoria Street, E.C. BRIGHTON: 135, North Street. Transcribers Note: Page 162 The following equation: ∴ _Z_ + _x´X_´ + μ´_W_ = ɑ_wW_ _Z_ = (ɑ_w_ - μ´)_W_ - _x´X´_ Is printed as ∴ _Z_ + _x₁X_´ + μ´_W_ = ɑ_wW_ _Z_ = (ɑ_w_ - μ´)_W_ - _x´X´_ in the original. End of Project Gutenberg's Colour Measurement and Mixture, by W. de W. Abney