The New Improved Slideing Rule

Robert Corson's Seal

Last updated 13 February 2021, David Green

Amongst the most interesting joint rules out there are those with a split personality - sector on one side and slide rule on the other - particularly the "New Improved Slideing Rule".

Having finally acquired one (below) I have been researching it as best I can (no maker's name). This appears to be the story.

Anonymous Improved Sliding Rule

Anonymous Improved Sliding Rule

The "manual" for these rules was "Mensuration Made Perfectly Easy by the Assistance of a New-Improved Sliding Rule". Editions dating from 1762 to 1819 are mentioned in WorldCat (

The "authors" of the various editions of the book included William Frost and Thomas Withnoll (1762-75*, 1762 and 1767 Edns), Robert Corson (1767-70*, 1771? Edn), Samuel Davis (1770-92*, 1770's Edn), Thomas Hughes (1787-97*, 1787? Edn), Thomas Smith (successor to the late Mr James Corson)(1792-1845*, 1794 Edn), and "the improver" in 1789, 1803 and 1819. [* dates when working, according to Clifton, Ref 3]

An even earlier edition of the book, "Wood and Lort's Mensuration Made Easy, 1757", was mentioned in Dash's 1820 sales catalogue [Ref 1, page 43] but is not listed in WorldCat.

The title of the 1767 edition mentions that the rules were "made and sold by W. Frost and T. Withnoll, successors to Wood and Lort (the improvers) ...". So I think we can comfortably assume that Wood and Lort introduced the design, some time in the early 1750's. Philip Stanley, quoted by Peter Hoop [Ref 2, p.79], says "a complete set of printed instructions, written by a John Browne, presumably the inventor of this rule, was available...". However, these instructions refer to the Scamozzi lines included on an earlier form of rule, a combination Coggeshall rule/sector, see section 2.

Catalogue entry

The layout of the rule is presented in the books. Below is an early example.

Mensuration Made Perfectly Easy-Rule

Both Wood & Lort and Robert Corson placed an unusual seal/logo on those of their rules that have survived. It would seem someone else introduced the drawing scales. If so, the earliest that would have been is perhaps Samuel Davis in 1770.

Later format of rule

The description of the scales on the rule, given in 1819 [Ref 16] was:

"THIS Rule is to Appearance, the same as the common Two-foot Sliding Rule with a joint; but instead of one Slide there are two, one sliding by the Side of the other in the same Leg, that by setting 1 on the lower side to proper Divisors it will readily perform all sorts of Gauging or Measuring whatever, each Divisor being figured with its proper Number, as 12 for Boards, 2150 for Malt Bushels, 144 for Timber or Stone, equal or unequal sided, &c.

On the other Leg on the same Face (instead of that obsolete Table which is commonly put there) are the lines of Chords, Hours, Latitudes, and Inclinations of Meridians, very useful in Mechanic Dialling; also on the same Leg is the four Scales of equal Parts, very useful for Drawing; on the other Face, between a Line of Inches in Eights, are MR. SCAMMOZZI's LINES, of great Utility to the Builder; on one Edge is a Line of Inches decimally divided, under which is a Line for finding the mean Diameter of a Cask, in the Form of the middle Frustrum of a Spheriod; and on the other Edge is the decimal Parts of a Foot."

Of Hours and Latitudes. TO MAKE AN HORIZONTAL DIAL.

Transcribed directly from [Ref 16, page 23]. (52 deg. 30 min. is about the latitude of Birmingham.)

"This Dial is the most useful of all, because the Sun stayeth upon it from its rising to its setting in all parts of the World.

It matters not what Form the Plane on which you would draw the Horizontal Dial is, whether it be round or square; but they are generally drawn round as on Plate 3. in which when you have drawn three Circles as a Margin to contain the Figures, draw the Lines CC, DD; which will represent the 12 o'Clock Line.

Note. The Reason of drawing two 12 o'Clock Lines is, to allow for the Thickness of your Stile, which may be made thicker or thinner according to the Distance you allow between those two Lines)

Later format of rule

The Arrangement of the Dialling Lines

The arrangement of the dialling lines by Wood & Lort was idiosyncratic. They chose HLCM (Hours, Latitude, Chords, inclination of Meridian). Later manuals revised this to HCLM. Yet the "standard" was MCLH as seen in the sectors below. Brass sectors made in the eighteenth century by Heath & Wing, T. Morgan, B Martin, M Berge, Dolland and J Sisson all used MCLH. Only John Gilbert chose to differ (HLCM). Brass sectors were replaced by elegant ivory sectors in the late 17th and early 18th centuries and every one of those I have seen (made by W&T Gilbert, Dudley Adams, G. Adams, Blunt, Troughton, Bate, Bleuler, Ramsden, M Berge, Elliot Bros, W. Elliott & Sons, J W Norie, and Dolland) used MCLH. This is rather more than a storm in a teacup: it may help with dating anonymous rules. This sector by W & T Gilbert shows the usual arrangement,

Dialling Sector by Gilbert

although it is easier to read on this scruffy Halse sector.

Dialling Sector by Halse

Opinions are divided about how common these rules are. Rees [Ref 4, page 106] says "At least five of these rules have been recorded: these are by Robert Corson 1767-70, and Samuel Davis 1770-92, both working in Wolverhampton; Wood and Lort (1750-60) and Abraham Hallsall 1773-80, both in Birmingham; and one unmarked." Five isn't many. I take this to imply they are quite rare.

Philip Stanley [Ref 5, p.216], quoted by Peter Hopp, says "This is an English pattern which saw significant production. Several examples have been found marked Sampson Aston, and one marked Z. Belcher (before or shortly after he immigrated to the United States). Unmarked examples also exist."

My impression is that they are rare. I have noted only nine at auction in the 19 years since 2002 (I could have missed some).

"New Improved Sliding Rules" sold at auction.
Date  Auction stock hinge the 2 slides dialling scales ruler maker condition
20020725 Ebay # 894544349 wood square brass,wood MCLH yes L>R Gough & Bowen ok
20050116 Ebay # 6504495464 wood square wood,wood HLCM no R>L Robert Corson good
20071015 Ebay #290168860941 wood arch brass, wood MCLH yes L>R Fairclough good
20120109 Ebay #270876316145 wood arch brass,wood HLCM yes R>L Watt of Boston fractured stock
20120929 David Stanley #495 wood arch brass,brass MCLH yes L>R anon good, 2ft 4-fold
20140310 Ebay #281278195571 wood arch brass,wood HCLM yes L>R anon broken brass slide
20140918 Ebay #111457706116 wood square wood,wood HCLM yes R>L anon good
20210114 David Stanley #1011 ivory square ivory,ivory HLCM no R>L Wood & Lort fine
20210126 Ebay #184628563162 wood square brass,wood MCLH yes R>L anon broken wood slide

Several more of the rules are mentioned in private collections. There is some double counting here: the 2012 David Stanley rule was purchased by Tom Wyman, and Rees' book possibly contains some rules owned by American collectors. For example, Rees' Wood & Lort may be George Gray's Wood & Lort, or the Corson rule on Ebay in 2005 may be the Corson rule mentioned by Rees.

Other Mentions of New Improved Sliding Rules.
 Source stock hinge the 2 slides dialling scales ruler maker remarks
A1 Rees, "The Rule Book" wood square wood,wood HLCM no Robert Corson 1767-70, Wolverhampton
A2 Rees, "The Rule Book" R>L Samuel Davis 1770-92, Wolverhampton
A3 Rees, "The Rule Book" Wood and Lort 1750-60, Birmingham
A4 Rees, "The Rule Book" R>L Abraham Hallsall 1773-80, Birmingham
A5 Rees, "The Rule Book" anon
B George Gray of Nashua Wood & Lort no picture [Ref 10]
C Wood & Lort no picture [Ref 11]
D History of Science Museum wood square wood,wood HLCM no R>L Wood and Lort says 1840. Date looks wrong.
E1 Tom Wyman, item 439 wood square brass,wood HCLM yes R>L anon
E2 Tom Wyman, item 455 wood arch brass,brass MCLH yes L>R anon 2-foot 4-fold!
F Hopp figure 43 wood square wood,wood yes Hassal Birmingham c.1797
G Hopp page 79 F. B. Cox in Toolshop auction 1999
H Philip Stanley page 216 Sampson Aston "several" !
I Hopp figure 46 wood arch brass,wood MCLH yes Sampson Aston
J Philip Stanley page 216 Z Belcher

This list extends the date when these rules were being made. Zachariah Belcher is listed as a box & ivory rule maker at 4, Bright Street, Sheffield in 1822 [Ref 6, page 304]. Sampson Aston (1833-1870) and F. B. Cox (1828-1862) push the date out to the 1830's or beyond.

My anonymous rule most closely matches that of Gough & Bowen (and, apart from the arch joint, Fairclough) suggesting a late manufacture. Annoyingly, neither of these makers is listed in Clifton, Rees or Webster [Ref 17]. However, both the names are mentioned elsewhere as plane makers. And plane makers sometimes made rules.

In the 1861 census Fairclough is listed as Robert Fairclough, age 48, plane maker employing 3 men, 1 apprentice, abode 72 Byrom Street, Liverpool. A blog on the web quotes from a book by Goodman ["British Planemakers from 1700" ?] (not seen)
Robert Fairclough & Co., 72 Byrom Street, Liverpool
1825: Plane maker, victualler
1847: Plane maker, edge-tool maker
1849: Robert Fairclough took over Samuel Lunt's premises
1883: Also at 130 Great Howard Street

Fairclough planes

Gough & Bowen are rather more mysterious. Two partnerships are recorded, in London and in Birmingham. They may be the same partnership. The first train from Birmingham to London ran on 17 September 1838, taking 5½ hours for the 181 km trip. Things could only have got better after that and being represented in both cities would have made sense.

In Birmingham, they seem to have been active from 1830-1859.

  • 1830 Salmon, Gough and Bowen, factors and wholesale ironmongers, 9 Moor Street [Ref 12,page 382]
  • 1 September 1830 partnership of Richard Salmon, William Gough and William Bowen dissolved [London Gazette]
  • 7 December 1856 partnership of Gough and Bowen dissolved because of death of William Bowen. [London Gazette, 27 December 1859]
  • 9 April 1859 partnership of Gough and Bowen dissolved because of death of Thomas Bowen. [London Gazette, 27 December 1859]

    No mention of rules, but they did make corkscrews!

    Gough and Bowen Corkscrews

    Meanwhile, in London they are mentioned as gunsmiths and as plane makers. Pollard lists them as gun makers in 1840 [Ref 13]. They made pretty and presumably deadly pistols.

    Gough and Bowen Pistols

    A number of dealers selling antique Gough and Bowen planes record them as active in London from 1840-1855. I have not found an authoritative source for these dates but they do tie in with Pollard and the Birmingham dates.

    Where does this leave my anonymous rule? With no maker's name, how to date it? Reordering what little information there is:

    (key: hinge(square/arch); slides(wood/brass); arrangement of dial scales (top to bottom); drawing scales (yes/no)); direction of measurement (left to right, or right to left)

    			 		early manual			? ?? HLCM N R>L
    		David Stanley #1011	Wood & Lort	1750-60		S II HLCM N R>L
    		Ebay #  6504495464	Robert Corson	1767-70		S WW HLCM N R>L
    		Ebay #270876316145	Watt Boston	1834-1849?	A BW HLCM Y R>L
    			 		later manual			? ?? HCLM Y R>L
    		Ebay #111457706116	anon				S WW HCLM Y R>L
    		Tom Wyman item439	anon				S BW HCLM Y R>L
    		Ebay #281278195571	anon				A BW HCLM Y L>R
    		my rule			anon				S BW MCLH Y R>L
    		Ebay #   894544349	Gough & Bowen	1830?-		S BW MCLH Y L>R
    		Ebay #290168860941	Fairclough	1825?-		A BW MCLH Y L>R
    		Hopp figure 46 		Sampson Aston 	1833-1870	A BW MCLH Y
    		Tom Wyman item455	anon				A BB MCLH Y L>R

    Most obviously, after Robert Corson the seal/logo was replaced by the (inch, three-quarter inch, half inch, quarter inch) drawing scales.

    More interesting, the arrangement of the dialling lines changed, first from HLCM to HCLM during the editions of the "manual", then to MCLH for the later makers. This suggests my rule is a later version, made in the 1800's.

    I seem to recall reading that for early English rules the inches measure was counted from zero on the right of the rule. Later the fashion changed to counting from the left (but Americans continued to count from the right). The list seems to support this idea but doesn't help much with dating my rule. Assuming the rule was made early in the MCLH period suggests a date of about 1820. Pretty tenuous.

    The Imperial Gallon replaced the Ale Gallon and the Wine Gallon in 1824. Gauge points for ale and wine would imply the rules were made before 1824 (assuming the rule makers were conscientious). All the rules that can be read have AG and WG gauge points. It all suggests my rule was made about 1800-1825.

    Most of the Ebay offerings provided very poor pictures of the rules, and for some of the other rules there are no pictures at all. However, Tom Wyman (1927-2014) had a superb collection, including two "New Improved Rules". Rod Lovett has created an archive of Tom's 576 items on the Oughtred Society's web site, at The rules are usually 2-foot, 2-fold but Tom's item #455 is special - a 2-foot, 4-fold rule:

    Anonymous Improved Sliding Rule

    Anonymous Improved Sliding Rule

    Section 2. Before the Improved Rule.

    What were the improvements?

    The Dialling Scales?

    Dialling scales were present on rules and sectors long before the New Improved Rule was introduced.

    Dialling is very ancient. Thomas Fale couldn't resist mentioning (nor can I) "The first diall that histories remember, is Lib.2.chap20 of The Kings in the Holy Scripture, where the Lord turned the Sunne back 10.degrees for Hezekias sake, whereby it had gone down in the Diall of Ahaz. This Ahaz was King of Jeruslem and reigned in the 3200. yeere after the creation of the World, and in the first Olimpiade of the Grecians, Afterward, as Plinie writeth, Anaximenes Milesius, the scholler of Anaximander first found out the reason and proportion of shadowes amongst the Lacedemonians and there taught the Art of Dialling." [Ref 15]

    Whatever. Writing in 1593, Fale doesn't mentioned the use of a rule. But John Brown in 1661 [Ref 8] had already introduced "A JOYNT-RULE fitted with Lines for finding the Hour of the Day, and the Azimuth of the Sun, to any particular Latitude ... Also the way of making any kinde of erect Sun-Dial to any Latitude or Declination, by the same Rule". This may not have been the MCLH arrangement but the placement of dialling lines on a rule was well established 100 years before the "Improved Rule".

    The Scamozzi Lines?

    The provision of Scamozzi lines on a sector dates back to before 1675 when John Brown wrote about them [Ref 9]. (1675 was the third edition). He had this illustration in his book and notes that "The said Rule with all other Mathematical Instruments are made and sold by John Browne, living in the Minories at the Sign of the Sun-Dial ...".

    Brown's Rule with Scamozzi lines

    And Henry Coggeshal1, in his "The Art of Practical Measuring" (1706), had this design for a carpenter's rule ...

    Coggeshall's Carpenters Rule

    I have never seen a rule with the above layout. More frequently the sector was replaced by a simple measuring face or with some drawing scales, as in the W Afston (Aston, about 1770) rule below.

    Aston's Carpenters Rule

    Aston's Carpenters Rule

    A more modern version of the 1706 design is this lovely rule by Gilkerson (about 1817?), with drawing scales replacing the load table.

    Coggeshall's Carpenters Rule

    Coggeshall's Carpenters Rule

    The Double Slide and Gauge Points?

    It seems the novelty of the rule was partly the inclusion of both these options on the one rule, but mainly the provision of the second slide and the line of gauge points.

    The gauge points on the few rules where they are legible are:

    Corson	Wyman	Wyman	mine	195571	"manual"
            #439	#455
    846*	816	816	816	816	816	816.75 "the superficial feet in a rod of one half-brick thick"
    359	359	359	359	359	359	359.05 "When you gauge Ale, set 1 on the lower slide to 359 for circular"
    282	282	282	282	282	282	ale gallon (AG equals 282 in3)
    	 27			 27
    231	231	231	31*	231	231	wine gallon (WG equals 231 in3)
    	  2			  2
    1728	1728	1728	1728	1728	1728	"cubic inches in a solid foot" (123)
    160	160	160	160	160	160     1 acre is 160 square poles
    144	144	14	144	144	144	gross "for stone or timber"
    -	 12	12	 12	 12	 12	"for boards"
    	 10		 10	 10
    	  9			  9
    294	294	294	294	294	294	294.12 "When you gauge Wine, set 1 on the lower slide to 294 for circular"
    2738	2738	2738	2738	2738	2738	Malt gauging: "the Divisor in Malt Round, Circular Inches in a Bushel"
    2160	2150	2150	2150		2150	Malt gauging: "the Divisor in Malt Square, Cubic Inches in a Bushel"
    183	183	183	183	183	183	183.34 "the circular inches in a superficial foot"

    * error? One of the charming things about old rules is that, being hand stamped, errors creep in. There are three errors in just the gauge points of these five rules. We are all only human.

    Section 3. A Quite Extraordinary New Improved Sliding Rule.

    In September 2017 an extraordinary joint rule was offered for sale on Ebay, and almost immediately withdrawn. It was a 4-foot 4-fold rule with four slides, three of brass and one of wood. It was in appalling condition with one brass slide missing and the others seized, the joints and iron tips rusted and the rule covered in dirt. The photos are awful but it is possible to discern that it was a combination Coggeshall/Routledge Engineers/Dialling rule with Scamozzi scales (and possibly more besides). I wonder why it was withdrawn and where it has ended up?

    Coggeshall Side

    Coggeshall part of rule

    Routledge Side

    Routledge part of rule

    Dialling Side

    This side is almost illegible, but not quite.

    Dialling part of rule

    Sector side with Scamozzi Lines

    Sector part of rule


    1. Thomas Dash: "Part II. 1820. A Catalogue of an Extensive Collection of Curious, Scarce, & Useful Books: In Antiquities, Topography, Natural and General History, Biography, Poetry, &c. with an Appendix, Containing a Small Collection of Theology, ... Now Selling at the Prices Affixed", Kettering, 1820,
    2. Peter M Hopp, "Joint Slide Rules", publ. Hexagon Press, 2009. ISBN: 978-1-906600-16-7
    3. Gloria Clifton, "Directory of British Scientific Instrument Makers 1550-1851." publ. Zwemmer, 1995. ISBN: 0 302 00634 6.
    4. Jane Rees and Mark Rees, "The Rule Book", publ. Astragal Press, 2010. ISBN: 13: 978-1-931626-26-2.
    5. Philip E Stanley, "A Source Book for Rule Collectors." Astragal Press, 2003.
    6. Edward Baines, "History, Directory and Gazetteer of the County of York" Vol 1 West Riding 1822.
    7. John Brown (Philomath), "The description and use of the carpenters-rule together with The use of the line of numbers commonly called Gunters-line : applyed to the measuring of all superficies and solids, as board, glass, plaistering, wainscoat, tyling, paving, flooring, etc., timber, stone, square on round, gauging of vessels, &c. : also military orders, simple and compound interest, and tables of reduction, with the way of working by arithmatick in most of them : together with the use of the glasiers and Mr. White's sliding-rules, rendred plain and easie for ordinary capacities
    8. John Brown (Philomath), "The Description and Use of a Joynt-rule: Fitted with Lines for the Finding the Hour of the Day, and Azimuth of the Sun & also the Use of Mr. Whites Rule for Measuring of Boards and Timber, Etc. publ. T. J. for J. Brown & H. Sutton, 1661 - [168 pages, with Diagrams.]
    9. John Brown (Philomath), "The Description and Use of an Ordinary Joynt-rule Fitted with Lines for the ready finding the Lengths and Angles of Rafters and Hips, and Collar-Beams in any Square or Bevelling Roofs at any Pitch, and the Ready Drawing the Architrave, Freize and Cornice in any Order. With other Useful Conclusions by the said Rule". 1675
    10. "For the past four decades, George Gray of Nashua, New Hampshire has collected a wide variety of both American and English rules. His display featured examples of American and English engineer's rules made of boxwood and brass with double slides. The earliest rule in his display was a Wood & Lort of Birmingham, England c. 1750 engineer's rule named "The New Improved Sliding Rule." This rule has dual adjacent Gunther brass slides." No picture. []
    11. "6. Boxwood two-foot rule, jointed, 12 by 1½ by ¼. In one limb are two adjacent slides with two 5½-inch radius scales in sequence. Wood & Lort, new improved sliding rule, Birmingham. About 1840." No picture (and wrong date). []
    12. Wm. West, "The History, Topography and Directory of Warwickshire", 1830
    13. Major H. B. C. Pollard, "A History of Firearms", 1926.
    14. History, Directory & Gazetteer of Yorkshire, Vol. I: West Riding, 1822 []
    15. Thomas Fale, "Horologiographia. The Art of Dialling: teaching an easie and perfect way to make all kinds of Dials vpon any plaine Plat howsouer placed: With the drawing of the Twelue Signes, and Houres vnequall in them all. Whereunto is annexed the making and vse of other Dials and Instruments, whereby the houre of the day and night is knowe. Of speciall vse and delight not onely for Students of the Arts Mathematicall, but also for diuers Artificers, Architects, Surueyours of buildings, free-Masons, Saylors, and others". London, 1593
    16. Anon, "MENSURATION MADE PERFECTLY EASY, BY THE ASSISTANCE OF A NEW-IMPROVED SLIDING RULE; Which, at one Operation, solves Questions in Superfices and Solids of all Denominations, By an entire new and concise Method, never before put in Practice. TO WHICH IS ADDED A DESCRIPTION & USE OF Mr. Scamozzi's Lines, IN FINDING THE LENGTHS AND ANGLES Of Raftors, Hyps, Collar Beams, &c. also Chords, Hours, Latitudes, and Inclination of Meridians, WITH THEIR USE IN MECHANIC DIALLING, Made and Sold (by the Improver)". Printed at T. CHAPMAN'S Office, No. 76, in Bull-Street, Birmingham 1819.
    17. Websters' Database of Scientific Instrument Makers,