1. This slide rules is used for cask gauging and is similar to the rule by Long.

2. One difference is that rather having a scale with two logarithmic cycles it has scale with 1 cycle (A) and brass plates on one end of each slide so that these can be used in one groove. This increases the accuracy of the rule, though adds to complication of using it.

3. The rule was made by Dring and Fage whose address is given as Tooley Street London. They were in this street but at different numbers for much of the 19th century. However the rule is embossed with the symbol of the Inland Revenue. The Board of Excise, responsible for duties on alcohol, was merged with the Inland Revenue in 1849, so this gives us a terminus post quem. In 1883 the company moved to The Strand; this gives us a terminus ante quem. Hopp says, p66, that they made an Excise Officers rule in 1868 so the rule is probably of around this date.

4. This rule came complete with a set of rods able to measure up to 50 inches. The rods could be screwed together and when this was done the alignment was very accurate. There was also brass plate which a rod could be screwed into but also a hole through which the rods could pass. The whole lot was in a leather carrying case.

5. For information on how such rules were used see here.

Rear view