1. This slide rule is used for calculating flow in sewers.
2. The rule is mentioned in Cajori's History of the Slide Rule. It is so far, in 2008, the only one of its kind to sold on eBay.
3. The patent on the rule was submitted in 1890 and granted in 1891. Arthur Honeysett was joint Patentee with Stanley, a well known instrument maker. The rule was mentioned in Stanley's advertisement in the 6th Edition of Pickworth's "The Slide Rule" published in1900. The rule was probably made between 1890 and 1900.
4. The rule has eight scales (see detail front right) labelled from A to H. B & C are on the slide the others are on the stock. Scale A is arranged to give the square root of the fifth power of the values on scale B. For example when the 1s are aligned, adjacent to the value of 2.0 on scale B you have 5.66 on scale A. This corresponds to Chezy's formula, which can be written:
Flow = C * Area * (Hydraulic mean depth * Gradient)0.5
where C is a constant and Hydraulic mean depth is the area of flow divided
by the wetted perimeter.
In many cases Area = C1 * Hydraulic mean depth 2
where C1 is also a constant (not the same as the above).
This gives Flow = C * C1 * Hydraulic mean depth 2.5 * Gradient 0.5
Hence the use of the power of 2.5 (i.e. square root of fifth power).
Scale C is a scale is inclination (gradient or slope)
Scale D is a scale of velocity
Scale E to H are scales of hydraulic mean depth for different classes of
sewers from 1, new and smoother, to 4, old and encrusted.
5. The slide had a cursor, now lost, whose design can be seen on the copy of a diagram from the Patent below. The cursor ran between two strips of wood screwed on to the top of the body of the rule.
6. The back of the rule had a printed sheet, now partially lost, with instructions for its use and tables for different shapes of sewers. These tables were also given in the patent application.
7. Arthur Honeysett was also a joint patentee of a method for improved aeration of sewage sludge in 1922. In the patent application Arthur Honeysett gives his place of residence as Buenos Aires. He is mentioned in scientific paper published in1896 relating to the sanitary works in Buenos Aries; he was assistant to the Principal Engineer and contributed to the paper.
8. The copy of the Patent was obtained from the UK Intellectual Property Office (www.ipo.gov.uk) who provided an excellent service.
Inventor's name
