Saturday, February 17, 2024

"Keep Within the Compass", Cautionary Prints, c. 1785

Here: a well off and contented woman,  her space defined by the compass which is encompassed by a circle.

The print, dated 1785, is now in the British Museum. Prints like this showing women and men within the circle, scribed by the open compass, with corner vignettes, were common c.1780.

 The woman is sheltered by the compass. She is in a tranquil country setting with her dog and her wealth, her book. Beyond the circle is the vivid story of her possible dissolution: drink and gambling leading her to debtors' prison where she must break hemp. 

The words on the circle are, "keep within the compass and you shall be sure to avoid many troubles which others endure". On the swing arm of the compass is engraved, "Fear God'.

Googling the phrase running around the circle, "Keep within the Compass" brings up this image and a description of Free Masonry, including the idea of the circle as a symbol for God. 

Whoever wrote the entry ignored that well made, shiny compass with a serrated, adjustable swing arm, tapered legs with well defined knobs and sharp points ready to scribe that circle. The commentary only says that it shelters the woman.

Why did the print maker draw a compass so carefully if it wasn't part of the visual message? A shiny shimmering circle would have sufficed. The compass is a tool; here the tool of God, and the tool required to draw the circle.

I think the writer, and we as a culture, have forgotten common skills and so we no longer understand references and images our ancestors took for granted. 

As recently as 1950, compasses were tools, used every day by people who built with their hands: masons, carpenters, as well as architects and designers.  This image is an illustration from Basic Technical Drawing, published by The Macmillan Company in 1956 and 1962, written by Henry Cecil Spence. 

70+ years later we have almost no experience of geometry as practical knowledge, of compasses as instruments.




When the 'Keep within the Compass' print was first made the designs in patterns books included geometry as a matter of course.

Plate XXXVIII in William Pain's pattern book,  The Practical House Carpenter, printed in London in 1794, assumed that his readers used geometry: "...the height of the column... to be divided into 9 equal parts, one of which will be the diameter of the column at bottom..." 

His description for the pediment begins, "to find the pitch of the pediment set the compass at a..." His readers understood the compass cues: the letters and the dashed lines, the notation of lengths on the line along the left side. 




Here is Plate X in Asher Benjamin's  pattern book, The Country Builder's Assistant, printed in Greenfield, MA, in 1797.

His descriptions include 'diameters', 'arch lines' and notes about where to 'set the compass'.  He writes, "Divide the height of the  column into 10 parts, one of which is the diameter of the column."

The compass was used for measuring as well as a layout.






This sculpture of James Watt. the Scottish engineer, carved about 1820, during his life time, shows him using a compass to design the steam engine.

The compass was an engineer's design tool.




James Watts' little compass is a measuring and design tool, a tool for thinking carefully, thoughtfully.


Here are 2 more historic prints of people within the compass and pictures in the corners of their desolution if they do not keep within the compass. 

 The gentlewoman is finely dressed with a devoted pup and a chest of jewels and garments beside her, a purse on her arm, a book in her hand. She keeps within the circle drawn by the compass. The sky is a lovely blue.

Clockwise from the upper right: The gentlewoman drinks, does not tend to her baby or her sewing.

She gambles and plays cards. losing her money.

The constable (in blue, an official someone) takes her off to debtors prison

where she must break hemp to help make the ropes for the English navy, and will be flogged if she doesn't.

 And, in case you needed reminding,  "Prudence produceth esteem".

Here is the gentleman, prosperous with land, servants, crops, a mill. He is finely dressed and well fed. 

In the corners are his downfall because he did not "keep within the compass": wine and women, gambling in the upper corners. 

His investments, his goods and ships, are lost at sea so that he too ends up in debtors' prison.


The final words: "Industry produceth wealth"







In case you wondered: God knows about compasses. Here He is creating the world, from the frontispiece of a  German Bible, c. 1250.







My thanks to Patrick Kennedy (of Historicorp and PTN)  who introduced me to these images several years ago.

To see the prints at a bigger scale look for the British Museum website and  'Keep within the Compass' online.








































   * William Pain, The Practical House Carpenter, 1794, 5th edition, London; Plate 38. Reproduction from British Library by Gale Ecco Print Editions




The ones sold as toys lack sharp points. They are useless because they skitter across the paper.  Without a fixed point for a center a compass can not draw a circle.

Tuesday, January 9, 2024

The Practical Geometry of the Parson Barnard House: Addendum


How did the builders of the Parson Barnard House actually use Practical Geometry?
Did they have to draw arcs with twine every time they wanted to measure something? 

Probably not. I think that they knew the geometry so well that they could take short cuts in laying out a house .*

Consider a carpenter's education in 1715, when this house was built.  A boy would have been apprenticed to a carpenter when he was about 11 years old. Along with woodworking skills he would have learned the fundamentals of geometry: how to use a compass and line for measuring lengths, how to lay out basic shapes with a compass and a straight edge. 

After 7 years of training the apprentice became a journeymen. He would have traveled and worked for other carpenters. He would have broaden his understanding of practical geometry and understood how geometry works. He would have been able to skip steps.


The previous posts on the Parson Barnard House** explored the geometry used to lay out the house frame and window locations on the front facade. 



The width chosen for the sill, about 18 feet, was the dimension used for the layout. The room sizes and the overall width and length of the house come from that first length. The bent's rectangle comes from using the sill length as the radius of the daisy wheel by which the framers laid out rectangles.



 The sill length was also the beam length for all the bents.  

The diagonals are the Lines which true the rectangle's corners and mark the location of the 2nd fl. beam. See earlier posts**




The chimney mass is the only part of the house with unrelated dimensions. Built of brick, it used the 3/4/5 rectangle.**


The carpenters would have staked a line at one end of the house for the exterior of the foundation 1-2.
Then they laid out the length, 18ft, and staked it 1-2. They laid out a right angle (here shown as a 3/4/5 triangle), and extended that line 1-3 18 ft. - marking the second side of the square; they didn't need to swing the arc. from 2 to locate 3, marking 3 corners of the square: 1, 2, and 3




The 18 ft. Lines arced from the corners 2 and 3 would cross, locating the 4th point. The carpenters didn't need to draw the arcs, just where they crossed.



Then they would check to be sure it was true, just as builders do today.


Matching diagonals across the square would confirm the carpenters' accuracy.  1-2 = 3-4

The Parson Barnard House geometry uses the length A for its floor plan and its bents. That length comes from the arcs of the length of the bent. It could have been found by 1) folding the Line (about 18 ft long, the length of the bent) in half, marking that point - shown here on the bottom line of the square  - and then 2) marking where the arcs cross (dot).  A length from the base to the arcs' intersection, the dashed line A, could be transferred to the side of the square, giving the width of a room, the height of the bent.  (NB: Geometry requires 2 points in order to draw a straight Line.) 

The carpenters only needed to find this length once. They could have marked it on a plank for reference until the frame was complete, then used the plank as sheathing for the walls or roof. 

Some of these layouts have been found and saved: Eastfield Village in East Nassau, NY, ( has some which they noticed on the roof sheathing when the Inn was dismantled and  moved to the site.  Unfortunately, because we have lost most of our understanding of practical geometry, those doing restoration rarely look for such notations left by earlier craftsmen. 

*NB: When I teach, the students and I swing the twine in arcs to mark the corners of a house foundation. It was easy, fun, and exciting as we see the shape come into being.  

** see: 

 *** Brick walls are built row by row. 2 Lines and the 3/4/5  keep them true vertically and horizontally.