1. This is a special rule produced for calculating velocities in sewers and pipes for given sizes and gradients.
2. Its binding gives the impression of being red leather.
3. The rule allowed the use of two different formulae; Kutter and Crimp & Bruges. Instructions in its use are given here.
4. The design has the registration number 508,576. From 1884 design registration in the UK followed a consecutive numbering system (unlike patents at that period). The first registered design in 1907 was 486,464 and in 1908 was 516,375. This dates the registration, and probably the rule, to 1907.
5. The pipe dimensions are those of a "standard" sewer. A newer shape was introduced before 1890. The use of the earlier cross-section helps to fix its date of manufacture toward the date of registration rather than later.
6. The address of the maker is given without a postcode. Postcodes were introduced in most big cities in the 19th century or early 20th, again suggesting an early date.
Rule closed
Gilt embossed name
Rule opened
Detail
Circular pipes
Detail
Egg-shaped sewers
Detail
Pipe dimensions
Detail -scales
Alternative scale
