The Gunter scale, for decades a valuable aid to engineers, surveyors, navigators, etc., has recently been entirely superseded by the "Mannheim " Slide Rule. This has nowadays proved itself to be indispensable in every office and to everybody whose business involves calculation.

Multiplication, division, involution, evolution and arithmetical, algebraical and trigonometrical functions can be performed on this rule mechanically with the greatest ease and rapidity and without mental strain.

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Kolesch's "Precision" calculating rule embodies a great improvement over other similar rules. It is made of the very best well seasoned built up mahogany stock with white celluloid facings. The graduations are all engine divided, clearly and accurately cut, and being on a white background are very legible. This is one great advantage of these rules over lithographed rules which are on the market, and which will wear off in a short time so that graduations and figures are illegible and indistinguishable.

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The main improvement, however, is the construction of the stock or body of the rule. The rules formerly constructed with celluloid facings on the inside of the groove only are always liable, under changes of temperature, climate or humidity, to expand, contract or warp, as shown in illustrations below.

In the Kolesch "Precision " slide rule this drawback is entirely overcome by mounting the two faces of the backbone with celluloid, as shown in figure below, making the body unaffectable by changes of temperature or humidity.

The ends of the celluloid facings on these rules are secured to the wood by German silver screws, which secure absolute adherence to the celluloid facings to the body of the rule. (See cuts above.) In order to meet every demand, these rules are manufactured five, eight, twenty inches long.

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Messrs. Kolesch & Co., 128 Fulton St., New York, gladly furnish any information and descriptive prices of "Precision " slide rules, also particulars of circular calculators.

The Atwater Kent Mfg. Works, 42 North Sixth Street, Philadelphia, Pa., manufacturers of ignition specialties, have introduced a new feature in their Automatic Volt Ammeters for 1906, which are now ready for the market. This is a "Dead Beat" needle, which, on account of its quickness in coming to rest insures a quick and accurate reading.

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Their meters are adapted to any work where primary batteries are used. Every meter is guaranteed absolutely accurate, hand calibrated to standardized ap-partus and thoroughly tested. A neat, hand-sewed leather case is furnished with each instrument. Price, 0-5 volts, 0-20 amperes, $5; 0 10 volts, 0-20 amperes, $7. Their voltmeters, which are the same in appearance as the Automatic Volt-Ammeters, but without button attachment, also have this excellent feature of the "Dead Beat" needle. Price, 0-6 volt, $5 ; 0-10 volt, $6. Price of ammeter, 0-10 amperes, $5; 0-25 amperes, $6; 0-30 amperes, $7. Meters with special reading up to 30 volts and 30 amperes, are made to order. these are very convenient and fully meet the requirements of automobile and gasoline engine users.