This paper was originally published in the Slide Rule Gazette, Issue 18, Autumn 2017 by the UK Slide Rule Circle.

An Unusual Alcohol Slide Rule

Introduction

In the latter half of the eighteenth century the standard slide rule used for assessing
the duty on wines and spirits was the Everard type with a nearly square cross-

The Unusual Rule

From time-

Figure 1

Figure 2

Unfortunately it is rather worn and does not photograph well so I will describe each
of the scales in turn, from top to bottom in each case. The first scale is in fact
two scales, one on the left hand side and one on the right; the left hand one runs
from 1 to 3.2 and is effectively the first half of a single radius logarithmic scale.
It has two gauge points with brass pins for the pre-

The next scales are on the upper half of the central strip and these are more unusual ones, at least on this type of rule. There are actually two scales, each occupying half of the length. The first (on the left hand part) is a single radius logarithmic scale folded at about 3.2. On it there are two gauge points, MS and MR, respectively for the side of a square vessel containing one malt bushel per one inch depth and for diameter of a cylindrical vessel containing one malt bushel per one inch depth. It is effectively a continuation of the left hand scale at the top of the rule, previously described. This is in fact the normal arrangement on one of the sides of a four slide Everard type rule.

The second scale, on the right hand half, is a reciprocal scale folded at 2150, the
number of cubic inches in a Winchester malt bushel. It is the malt depth scale and
labelled MD. Below these scales is a double radius scale marked 1-

The reverse of the rule has the variety scales for spherical, second and third varieties and the associated inch scale representing the difference between the head and bung diameters of the cask. The rule measures 12 x 1.6 x 0.4 inches.

Conclusion

This rule differs from other single sided, dual slide, slide rules previously described. On the one face it in fact has all the usual scales found on a four slide Everard type rule. Clearly these are compressed compared to a twelve inch Everard type rule so the resolution and accuracy are reduced in proportion. The presence of the variety scales on the reverse means this rule can carry out all the functions required by a gauger.

Acknowledgements

I am very grateful for the help provided by P A (Tom) Martin in identifying the functions of various parts of this unusual slide rule.

1. David M Riches, The Missing Link, Bulletin of the Scientific Instrument Society
No.115, December 2012 and the Slide Rule Gazette Issue 14, Autumn 2013. The slide
rule illustrated here is a post 1824 one with Imperial gauge marks but the construction
of the pre-

2. Thomas Wyman, SOHO Steam Engines, The First Engineering Slide Rule and the Evolution
of Excise Rules, Proceedings of the 18th International Meeting of Slide Rule Collectors,
pp 63-

3. Jane Rees and Mark Rees, The Rule Book -

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