Page:The slide rule; a practical manual by Pickworth, Charles N.djvu/124

xi ADVERTISEMENTS Tavernier-Gravet Slide Rule CELLULOID SCALES. . . GLASS CURSOR £ s. 10 in. (2Sc/m) Tavernier-Gravdt Slide Rule, engine divided scales on white celluloid, glass cursor in metal mount .0106 Case extra, Is. 6d. ; postage 3d., or to the Colonies, Is. 6d. 5 in. (12*5 c/m) Tavernier-Gravet Slide Rule, celluloid scale, glass cursor. . . . . . . . 10 6 Do. do, do. 15 Case extra, 2s. Do. do., do. in wood case. . . . . . . 2 10 14 in. (36 c/m) 20 in. (50 c/m) SOLE MAKER OF HALL'S NAUTICAL SLIDE RULE Designed to save the navigator the labour of arithmetical calculation and the use of tables when reducing the ex-meridian and finding corresponding errors in Latitude and Longitude, etc., etc. With instructions in case. . . 17s. 6d. SOLE MAKER OF THE R.H.S. CALCULATOR A spiral logarithmic scale, 50 inches long, wound upon a cylinder, 8 inches long and about 0*75 inches in diameter. A fourth figure in a number can be read by eye division. Designed and patented by Professor Robert H. Smith. (New Model in preparation) CATALOCUE. PART IV. Surveying, Mathematical and Nautical Instruments, including Theodolites, Tacheometers, Levels, Pocket Telemeters, Clinometers, Prismatic and I, uminous Compasses. POST FREE ON APPLICATION • J. H. STEWARD, OPTICIAN to the BRITISH and FOREIGN GOVERNMENTS 406 & 457 Strand, LONDON Telegraphic Address: "TELEMETER,'' LONDON TELEPHONE: 1867 CERRARD