Nature . e ought to do).—Grant Allen in Kncnvledge. The Platyscopic Lens is invaluable to botanists, mineralogists, or ento-mologists, as it focuses about three times as far from the_ object as theCoddington Lenses. This allows opaque objects to be examined easily. The Platyscopic Lens is made of four degrees of power, magnifyingrespectively lo, 15, 20, and 30 diams. ; the lowest power, having the largestfield, is the best adapted for general use. The Lenses are set in Ebonite Cells, and mounted in Tortoiseshell Frames. Price of the Platyscopk Lens, mounted in Tortoiseshell, magnifying either
Nature . e ought to do).—Grant Allen in Kncnvledge. The Platyscopic Lens is invaluable to botanists, mineralogists, or ento-mologists, as it focuses about three times as far from the_ object as theCoddington Lenses. This allows opaque objects to be examined easily. The Platyscopic Lens is made of four degrees of power, magnifyingrespectively lo, 15, 20, and 30 diams. ; the lowest power, having the largestfield, is the best adapted for general use. The Lenses are set in Ebonite Cells, and mounted in Tortoiseshell Frames. Price of the Platyscopk Lens, mounted in Tortoiseshell, magnifying either 10 \s 20 or-^o diaiiteters, eacit/lO^ver, 15s. /« nickelised German Silver, each /?oioer, 17s. 6d. Illustrated Description sent free. JOHN BROWNING. 63 STRAND^ LONDON, ^reseivts, NEGRETTI &. ZAMBRAS SELF-RECOKDING METEOROLOGICAL INSTRUMENTS. THE THERMOGRAPH, for Outdo Observatii Thi~ Instru-i mountedin a JapannedMetal Case withGlass Front, andgives continuousrecords on Chartfv. Accurate Thermometeis for all nnrposes. Special Illustrated Price List of Instruments,suitable for Presents, free by post. NEGRETTI & ZAWIBRA,38 HOLBORN VIADUCT, ranches: 45 CORNHILL, and 122 REGENT STREET, London. liv NATURE [December 15, 1898 ROYAL INSTITUTION OFGREAT BRITAIN, : .STREET. JICCADILLV, \V. Centenary Year of the Royal Institution, 1899. LECTURE ARRANGEMENTS BEFORE EASTER, 1899. Lecture Houk, 3 oclock CHRISTMAS Robert Ball, , , , Lowndean Professor of-Astronomy, University of Cambridge. Six Lectures (adapted to a JuvenileAuditory) on * Astronomy. On December 27 (Tuesday), December 29, 3 • 1808 • January 3 5, 7, i**- ^— ^— * ^— u:ij_„„ —i— c. tecn/Half-a-Gumea. One Guinea the Course ; i.,hildren under Su Prof. E. Rav Lankesteb, , , F , Director of British-Museum (Natural History), Kullerian Professor of Physiology, TenLectures on The Morphology of the Mollusca. On Tuesdays, January Fe
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