Slide rules HOME page  COLLECTION  NONSTANDARD RULES 
Make  Elliot, London  
Model  Soho rule  
1. This is known as a "Soho" rule after the district of
Birmingham where James Watt (of steam engine fame) and his partner Matthew Boulton worked.
They are normally credited with the development of this rule. See the other Soho rule for more detail. 2. In this rule I, unfortunately, had the slides on the wrong faces of the rule when I scanned it. In reality the front of the rule would have had the "classic" A, B, C (2cycle) and D (1cycle) scales. The sine and tan scales would have been between the two A (2cycle scales) 3. The combination of A, Sin, Tan and A scales would cover the range 0.6º to 45º for the tan scale and 0.6º to 90º for the sine scale. It would have been possible to do simple calculations using the trigonometrical scales without a cursor. 4. Some of the "gauge points" seem a bit strange. (In fact they are not gauge points but settings of the rule to get a factor similar to the use of 22 and 7 for pi). For example, using 81 gallons to 13 cubic feet gives a ratio of 6.23 whereas 25 gallons and 4 cubic feet gives the exact value of 6.25. It could not have been due to the use of either the wine or ale gallon as both of these had a larger difference the between 62.5 and 62.3. 5. The maker, Elliot, was at the address shown in London in from 1840. Given that fact it is interesting that the rule refers to Wine gallons some 16 years after they became obsolete. This rule is from the collection M Taylor. 

Front view 

Detail front left 
Detail front right 

Detail back 

Detail  back left 
Detail  back right 

Detail  maker's name 
Detail conversion 
Detail  Chord scale 
Manufacturing date  cd 1850  
Length  12"  
Material  Boxwood  
Scales  See above  
Cursor  None 