GB191228546A - Improved Appliance for use when Teaching Astronomy, Navigation or Geography. - Google Patents

Abstract

28,546. McEwan, D. Dec. 11. Maps and charts.-An appliance for use in teaching astronomy, geography, or navigation comprises a framework adapted to carry or receive a series of combined astronomical and geographical charts showing parts of the earth's surface and the stars overhead at these parts for a particular time. The stars are represented on the charts by perforations x, Fig. 1, and the charts may be made of semi-transparent material to allow the geographical features to be more clearly seen. Since the observer is supposed to be standing at the centre of the earth, the geographical features are shown reversed. The chart shown in Fig. 1 is drawn for a person standing at the centre of the earth and looking through a point at 33¢ degrees north latitude. In use, the observer is supposed to be standing perpendicular to the position for which the chart is drawn, that is, at the centre of a plane k, and to be looking north. The line k thus represents his horizon, and stars and portions of the earth's surface below the line k are below the horizon. In order to give a more realistic appearance to the plane k, an ellipse k<1>, which may be coloured, may be drawn on the chart to give an idea of a plane in perspective. The charts may be arranged upon an endless band carried by rollers b, c, or may be inserted in one or other of the pockets p, o, Fig. 3, of a case consisting of a central plate l provided with a circular opening l<1> and plates m, n, of celluloid which may have lines of latitude and longitude thereon. In a modified case, two pockets are arranged one behind the other, so that either one chart may be used as described above, or two charts, one bearing a geographical map and the other a star map. may be inserted one behind the other.