Make Rabone and Sons, England
Model Routledge Engineer's rule
1. The Engineer's rule designed by Routledge was one of the major since Coggeshall first developed a rule of in the "2 fold, 2 foot format". The design was introduced in 1808.
2. Routledge had his own ironmonger's business in Bolton. (An ironmonger is a seller of, usually small, tools and items such as screws and nails). He spent the last few years of his life in Poland. (see Peter Hopp, Slide Rules their History, Models and Makers).
3. One big difference between this rule and the Coggeshall rule is the arrangement of the "slide rule" scales. The A, B and C scales (2 cycle logarithmic) is the same but the D scales (single cycle logarithmic) runs from 1 to 10 whereas on the Coggeshall it runs from 4 to 40.
4. The final image shows the scales in close up, with A at the top and D at the bottom. As can be seen the scales labelled B and C scales are effectively a sing;le scale. This was a way of enabling the D scale to be used with the A and B scales before the invention of the cursor.
5. The measuring scales are similar.
6. The other major difference is that the tables for money calculations have been replaced by tables of gauge marks. There are effectively 4 types of gauge marks:
  • A series of gauge points for square shapes, cylinders and spheres. These are in 7 columns: FFF where all dimensions are in feet for square shapes, FII for square shapes where length is in feet other dimensions are in inches, III for square shapes where all dimensions are in inches, FI for cylinders where length is in feet and diameters is in inches, II for cylinders where both dimensions are in inches, F for globes (spheres) where the diameter is in feet and I where the diameters is in inches. The first two lines relate to volume in either inches or feet, thus is possible to get the volume in cubic feet from dimensions in inches and vice versa. The next three lines relate to volume measure for "old wine", "imperial gallon" and "water". The phrase to "old wine" refers to the period before 1824 when a wine gallon was not the sakje as an ale gallon. Then follow 12 lines of gauge points for different metals and other solid objects.
  • Gauge points for regular polygons.
  • A set of gauge points for circular measurement.
  • The final set of gauge points is for steam engines. Early steam engines operated at low pressure and these gauge points relate to engines at 7 pounds per square inch (psi).

7. The maker Rabone was founded in 1784 and only stopped making slide rules in 1963. They still make other types of rules.

8. I also have a Routledge Engineers' rule made by Thomas Bradburn and Son. Their logo is given below. Unfortunately this rule is no easier to date than the other. The logo was registered in 1832 but it was in use by that company and their successor until 1909. (Information from Peter Hopp).

Front view
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Back view
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Maker's name
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Name of inventor
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Gauge points for volume and weight
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Gauge points for volume and weight
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Gauge points for polygons
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Gauge points for circles and steam engines
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Scale arrangement
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Logo of Thomas Bradburn and Sons

Manufacturing date This is difficult to estimate. The rule appears to have been extensively cleaned so has little sign of the patina of age. The fact that the rule refers to "old wine" suggests that it was made in the period immediately after the change of units in 1824. The use of low pressure for steam is also indicative of an early date.  In the Mechanic's Assistant, a U.S. publications of 1849, gauge points for 7 and 10 psi are given. On the other hand Rabone made slide rules until 1963 and it may have been that they never got round to updating the table of gauge points. All that can said with certainty is that it was made in the century following 1824.
Length 12"
Material Boxwood and brass
Scales Non-standard but A,B are 2 cycle logarithms equivalent to those on modern rules,C is identical to B and D is a single cycle logarithm equivalent to D on modern slide rules.
Cursor None