Palladio Londinensis' Frontispieces, c.1755

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Reader beware: This post is a work in progress.  I thought this was a simple post: I wanted to share the 'Diameters', because visually, with no words, they show how Practical Geometry was used.   

However, I am also reading James Gibbs' Rules for Drawing the Several Parts of Architecture..." * I found I was comparing of English pattern books c.1755. It was too much for one post. I edited. 

This post is about Salmon's illustrations. I've written a companion piece using James Gibbs' engravings.

These engravings are from Palladio Londinensis,The London Art of Building,  a builder's manual produced and published by William Salmon from 1734 to 1755.  Salmon was a carpenter and builder northeast of London. His book was readily available in bookshops and libraries in Britain and  the Colonies from the 1750's into the early 1800's.**

 

 

William Salmon's  Composite Order, Plate XXVI 

He wrote "..the Height of the Door is 3 Diameters, and hath a manner of pannelling different from all the foregoing; also the Entablature is 1/5 the length of the Pilaster, as may be seen from the Circles." 

The diameters Salmon mentions have no numerical value, nor do the Circles. They are the proportions for the door: 1wide/3 tall, and then for the pilasters and the entablature (the part of the door frame above the door itself and below the pediment): 5/1.  

A builder would have known generally how much space - width and height - he had to work with.  The circles and the diameters (semi-circles) were units of measure, the 'module' for that door's layout and design. Stepping off the module and adjusting its length, ie: its diameter, to fit the space he had, the builder could find the actual lengths of the door, its surround, and the entablature.** The layout of the frontispiece, the piece at the top, could come later. 

 

Before standardize dimensions, lengths were 'stepped off' using a compass. The diameter is the visual symbol of the compass' span and the act of swinging it. Salmon's book included drawings of diameters in rows - 'stepped off'. 

This illustration, from a 1950's text book for technical drawing, shows the compass stepping off 3 times.  

 

 

 The 'Doric Order Frontispiece and Door, Plate XXI'.

The height of the entablature is set by the length of the pilasters. The diameters on the right side, the modules, divide the length of the pilasters into 4 parts. 1 more part is added for the entablature.

The pediment is laid out by Vignola's Rule**  

 Salmon gives no geometric relationship between the door's proportions and the pilasters.

Is the circle drawn on the door its module? 
The door's length is 2 large circles plus a small one. The upper large circle encloses 4 small circles, so the whole door is 9 small circles tall. 

How would a carpenter find the diameter for the smaller circle if he began with the large one? It can be done, but not easily or quickly. Using the small circle as the module would be easier.

 The geometry:  Lay out 4 circles on a line. The length of the line from the outside edge of the first to the outside edge of the last is the large circle's diameter.

The point where the 2nd and 3rd circles cross the line is the center of the large circle. The circle's radius is the length of the line from the center to the outside edge of the first small circle.

Using his compass the builder could step off 4 small circles, or one big one for the width of the Dorick door, and 9 small circles for its height.

 

This 'Corinthian Order, Plate XV' door is 2-1/2 circles. The surround is 5 circles, the entablature is 1. 

The geometry of the door,  2-1/2 circles does not determine the size of the lower panel, the upper opening, or the size of the panes of glass. Salmon doesn't seem to understand that these sizes could have been derived from the proportions of the door itself. 

There is no indication that the pilasters' width or height might have been chosen to be in proportion to the door, or vice versa.

 

 

 

'A Dorick Entrance, Plate XXII' is an arched entry without a door, 5 modules long and, as the circle tells us, 3 modules wide.

The capitals of the pilasters around the arch are located at the center of the big circle. But the columns on each side of the opening and their pedestals do not use the proportions of the entry's 5 small circles.   

 

 

Here is the very simple geometry: the 3 circles.

 

 

Since each was drawn with a compass, each has a center. Therefore the big circle which encloses them is easy to draw; it has a radius  of 1-1/2 little circles.

 

London and the Colonies in the 18th C. needed builders. Some were well trained; others not quite.  Along with instructions for laying out Entrances, William Salmon's book included chapters on 'Geometric Problems', 'Prices of the Labor and Materials' for the trades as well as 'all sorts of Iron Work', information about staircases, lumber, roof framing, 'Chimnies', and the 5 Orders of Columns. 

The polite conclusion is  that Palladio Londinensis helped builders educate themselves, that in spite of its shortcomings it was a useful reference. Even so, I find his explanations inadequate and sloppy.

 

* James Gibbs, Rules for Drawing the Several Parts of Architecture..., London, 1753. The print and drawings are clearer and much easier to read online. 

**My copy:  Salmon, William, Palladio Londinensis,  London, 1755, Gale Ecco reprint. The original is often found in historic libraries. One is in the library of Gunston Hall, in Virginia, .

***Today doors and their surrounds come in standard sizes. Before the Industrial Revolution, a door and its frontispiece might be match another next door, or not. 

**** See my blog posts about Andeas Palladio's 'module',  https://www.jgrarchitect.com/2024/05/a-daisy-wheel-is-module.html, and https://www.jgrarchitect.com/2020/04/practical-geometry-lesson-3.html

***** Yes, I wrote a post about that too: https://www.jgrarchitect.com/2024/05/how-to-layout-pediment-350-years-of.html