[34] These instruments, and the others here noticed, are supplied in this country by Mr W. F. Stanley, the noted scientific instrument maker of Great Turnstile, Holborn, London. They are described in his treatise on “Mathematical Drawing Instruments,” from which work, it should be stated, some of the present notes concerning them are derived. A source of accurate information on the theory of planimeter, to which Mr Stanley himself expresses indebtedness, is the paper by Mr —now Sir—F. J. Bramwell, read before the British Association in 1872, and contained in the Association Reports for that year. [35] The following is a list of the multipliers for converting the planimeter readings to square feet for any required scale:— 1/16-in. scale = 256 ⅛-in. do. = 64 3/16-in. do. = 28·44 ¼-in. do. = 16 5/16-in. scale = 10·24 ⅜-in. do. = 7·11 ½-in. do. = 4·00 ¾-in. do. = 1·77 1-in. scale = 1·00 1½-in. do. = ·44 3-in. do. = ·111 BOOKS RELATING TO APPLIED SCIENCE PUBLISHED BY E. & F. N. SPON, LONDON: 125, STRAND. NEW YORK: 35, MURRAY STREET. _A Pocket-Book for Chemists, Chemical Manufacturers, Metallurgists, Dyers, Distillers, Brewers, Sugar Refiners, Photographers, Students, etc., etc._ By THOMAS BAYLEY, Assoc. R.C. Sc. Ireland, Analytical and Consulting Chemist and Assayer. Third edition, with additions, 437 pp., royal 32mo, roan, gilt edges, 5_s._ SYNOPSIS OF CONTENTS: Atomic Weights and Factors—Useful Data—Chemical Calculations—Rules for Indirect Analysis—Weights and Measures—Thermometers and Barometers—Chemical Physics—Boiling Points, etc.—Solubility of Substances—Methods of Obtaining Specific Gravity—Conversion of Hydrometers—Strength of Solutions by Specific Gravity—Analysis—Gas Analysis—Water Analysis—Qualitative Analysis and Reactions—Volumetric Analysis—Manipulation—Mineralogy— Assaying—Alcohol—Beer—Sugar—Miscellaneous Technological matter relating to Potash, Soda, Sulphuric Acid, Chlorine, Tar Products, Petroleum, Milk, Tallow, Photography, Prices, Wages, Appendix, etc., etc. _The Mechanician_: A Treatise on the Construction and Manipulation of Tools, for the use and instruction of Young Engineers and Scientific Amateurs, comprising the Arts of Blacksmithing and Forging; the Construction and Manufacture of Hand Tools, and the various Methods of Using and Grinding them; the Construction of Machine Tools, and how to work them; Machine Fitting and Erection; description of Hand and Machine Processes; Turning and Screw Cutting; principles of Constructing and details of Making and Erecting Steam Engines, and the various details of setting out work, etc., etc. By CAMERON KNIGHT, Engineer. _Containing 1147 illustrations_, and 397 pages of letter-press. Third edition, 4to, cloth, 18_s._ _On Designing Belt Gearing._ By E. J. COWLING WELCH, Mem. Inst. Mech. Engineers, Author of ‘Designing Valve Gearing.’ Fcap. 8vo, sewed, 6_d._