James Gibbs' Rules for Drawing the several Parts of Architecture

My previous post looked at Palladio Londinensis' instructions for the use of geometry to design of entrances.* I found that essential information necessary to the layouts was left out/ not understood/missing.  Given that background, reading and writing about this book by James Gibbs has been a pleasure.

 

RULE for DRAWING the several PARTS of ARCHITECTURE

IN A More exact and easy manner that has been heretofore practiced by which all FRACTIONS, in dividing the principal MEMBERS and their Parts, are avoided.

 
By JAMES GIBBS

The Third Edition, 

London      1753**

This is a small book, 28 pages of text, 64 engravings. Gibbs is simplifying the design of columns. He discusses the complexity of dividing a module (the diameter of given circle) into minutes and seconds; that it's difficult to "divide the small parts with a compasses" and may "occasion mistakes".

He starts, "Of Columns and their Measures". The heights of columns are listed:  "The Tuscan - 7 diameters. The Doric - 8 Diameters. The Ionic - 9 diameters. The Corinthian - 10 diameters. The Roman or Composite - 10 Diameters." Next he discusses Entablatures, then his 64 Plates.

I am curious about how did masons and carpenters working on ordinary vernacular buildings use Practical Geometry. Can Gibbs' engravings tell me about vernacular design c.1730-50?  

Here are Gibbs' notes on 6 doors.

 

Plate XXVII shows 3 door frames: Tuscan, Dorick, and Ionick.

Each door has a segmented line on the left side. The divisions start at the top of the base of the columns. The Tuscan and Dorick lines both have 5 sections, one of which is the entablature's height.

The Ionick door has 6 sections, one of which is the entablature.

 

Those sections are the modules for all the parts of the door. The module is a length, a diameter of a circle drawn by a compass. So how does builder choose how big to make it? Where does he begin? 

Gibbs writes, "First find the Diameter of the Column, give 6 Diameters from middle to middle of the Columns..." 

From that diameter comes the sizes: the spacing of the columns, the width and height of the door opening. The door frame is a 'semidiameter', half a diameter, a radius.

 

Gibb's drawings are spare, clean.  His explanation, The Ionick Door, Plate XXXVII, second paragraph, for "The Geometric Rule to find the height of the Pediment..."  is easy to follow. ***

 

Vernacular buildings in the Colonies had doors with similar entablatures. Do the entrances for the Rockingham, VT, Meetinghouse follow Gibbs' instructions?  I will check.

 

 

 

Gibbs' Plate XLII,  'Three Doors with Archtraves'. 

Gibbs focuses on the architraves. I am looking at the doors. I want to know if our American builders use these rules to layout doors.****

The doors begin with a square whose length is the width of the door. The diameter of the square is divided into 6 parts. One part is the width of the frame, the Architrave, which today we would specify as the molding or trim. The middle door is taller: it adds one more part (1/6) to the width and height of its trim. The diagonal of both squares "gives the bigness of the pilaster upon which the Scroll is fixed."

 

The geometry for dividing a diameter - or any line - into 6 equal parts:

Using your line as the length of the sides, draw a square. 1) Add the diagonals . 2) Add the center lines. 3) Add the 4 lines from corner to opposite center point. Note the points where the  lines intersect.  4) Connect those points with lines.

You have divided the square into 3 long rectangles, and your line into 3 equal parts. See '1/3,1/3/1/3' above the square.

The distance between the center line of the square and the closest vertical line is 1/6 of your line . See "1/6" below the square, lower right. 

                                                                                                                  

 

*  https://www.jgrarchitect.com/2024/12/palladio-londiensis-frontispieces-c1755.html

**I am reading this through the University of Notre Dame  https://www3.nd.edu › Gibbs-Park-folio-18 

The first edition was published in 1732. It was available for purchase in the Colonies. I am always interested to see what words and phrases are capitalize in books printed in this era. 

***For  more information about pediments see my posts about Vignola's Rule for Pediments 

**** Today, a builder has a catalogue of doors to choose from. The doors may look different, but their widths and height are  similar: exterior doors are 3' x 6'8", 3'x7'. Other sizes must be special ordered or custom-made.  Before the Industrial Revolution there was no such uniformity.