Part 40

JOHN DAVIS & SON (Derby), Ltd. ALL SAINTS’ WORKS, DERBY

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K & E Slide Rules

are constantly growing in popularity, and they can now be obtained from the leading houses in our line throughout the United Kingdom.

We manufacture a complete line of ENGINE-DIVIDED SLIDE RULES, and call special attention to our Patent Adjustment, ensuring smooth working of the Slide; also to our new “Frameless” Indicator, which hides no figures on the Rule.

THACHER’S CALCULATING INSTRUMENT, for solving problems in multiplication, division, or combinations of the two; has upwards of 33,000 divisions. Results can be obtained to the fourth and usually to the fifth place of figures with a surprising degree of accuracy.

We also make

ALL METAL, CIRCULAR, STADIA, CHEMISTS’, ELECTRICAL, and OTHER SPECIAL SLIDE RULES DESCRIPTIVE CIRCULARS ON REQUEST

KEUFFEL & ESSER CO. 127 Fulton St., NEW YORK General Office and Factories, HOBOKEN, N.J. CHICAGO − ST. LOUIS − SAN FRANCISCO − MONTREAL

DRAWING MATERIALS MATHEMATICAL and SURVEYING INSTRUMENTS MEASURING TAPES

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NORTON & GREGORY LTD.

Head Office

CASTLE LANE, WESTMINSTER, LONDON, S.W. 1

Branches

71 QUEEN STREET, GLASGOW. PHOENIX HOUSE, QUEEN STREET and SANDHILL, NEWCASTLE-ON-TYNE.

SLIDE RULES in Stock, from 17/6 to 27/6

Special Quotations to the Trade for Quantities

For particulars of Surveying, Measuring and Mathematical Instruments, Appliances and Material of all kinds for the Drawing Office, write to the Head Office.

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NORTON & GREGORY, LTD., London.

“DIAMOND” DRAWING INSTRUMENTS Manufactured at our London Works.

CENTRE SCREW SPRING BOW HALF SET.

4 inch Spring Bow Half Set centre screw adjustment, with interchangeable needle, pen, and pencil points Price 17/6

The Centre Screw Spring Bow Half Set of Compasses, as illustrated, possesses the advantage of COMBINING IN ONE INSTRUMENT THE SET OF THREE SEPARATE SPRING BOWS hitherto in use, while the centre screw makes for ease and accuracy of manipulation, at the same time providing a radius of over 2 inches, or double that of the old pattern.

This instrument is less expensive than the set of 3 bows, while considerably stronger in construction.

The fixed needle point is shouldered.

This illustration is given as an indication of the various Drawing Instruments manufactured by us.