The second menagery in James Gibbs' On Architecture* was never built. In Part 1 of 2, I wrote about the first one which was built at Hackwood Park, an estate near London. It is still standing.
Here is Gibbs' portrait with his compass, the mark of his profession.
Gibbs' expected "any Workman who understands Lines" to be able to execute his designs. What would a workman have seen in Gibbs' drawings? What could I see? Did I understand Lines?
The first option was so simple. I was looking for an equally direct layout for this second design. I could find only complex solutions. They worked, but they were not direct. For 3 months the obvious design was right there and I couldn't see it. I put the puzzle aside several times.
This 'menagery' was to be a welcome destination for those strolling through the Hackwood Park estate grounds. Built of stone, the menagery would not have been as dark as this image.The 'draught' elevation accentuates the quoins and articulated arches, to give the workmen the necessary information.
Like the design which was built, the pavilion required a gracious porch with a room on each side: one for serving and drinking tea, one for the quiet perusal of books about nature, especially birds. The living quarters for the staff who took care of the estate's pheasants were around the back.
Today a plan usually lays out the exterior dimensions. Here the exterior is to be stone, perhaps ashlar or split, with rusticated, oversized arches and quoins (the corner blocks). Using inside dimensions to layout the plan allowed the exterior dimensions to vary.
Note that Gibbs' drawing of the exterior stone facade is structural. The blocks interlock on the corners; the arches and key stones interlock with the wall.
The floor plan begins with the central form: the porch and caretaker's
quarters. Its size is determined by 2 3/4/5 rectangles overlapped at
Gibbs assumes the workmen who might copy his 'draught' know how to build walls; he is not providing a construction document.
A workman could true his rectangle to center the doors on the walls. Note the red line.
The lines from the corners to the center locate the center lines for the arched columns.
I have left out many lines here for clarity. They could be added to check the work.
I call this 'The rule of Thirds' because artists who use these lines as a design tool call it by that name. It's the 3x3 pattern that appears when we edit cellphone pictures. **
The wings of the menagery are set back 1/4 of the depth of the main block in the front and the back - note the red line with arrows As the geometry here is the 3/4/5 rcctangle it is fitting that the wings' length is proportional to the main pavilion's length: 6/8 or 3/4.
The wings are themselves both 3/4/5 rectangles.
The 3/4/5 rectangIe was a common way to add a wing to an existing building. If the mason set his length against the central form at 4 units and his width at 3 units, his wing would be square against the main block. His stone work would be true. I have drawn the 3 x 4 units here. I have also left my pencil marks for further information (enlarge the drawing!)
While this menagery design is more complex to write about than Gibbs' other design*, it is quite easy to lay out with a compass and straight edge. A trained workman would have known the steps. The 3/4/5 rectangle and the Pythagoras Theorem are used today.
The elevation? It's 4 squares and the same pediment layout that Gibbs used on the menagery design which was built. The inside dimensions govern. The red arcs drawn show the floor width of the rooms are also the height of the elevations.
A note: the windows are centered on the rooms' inside wall, but not on the exterior width of the wing. The quoins are such a strong visual vertical that they appear as an anchor. The windows were centered on the rest of the wall.
The pediment is drawn following the rules described by Serlio. For step by step instructions, refer to Part 1 of 2 of this post of the draughts for the Menagery.*
* Gibbs' book On Architecture, published in 1728, includes 150 plates: plans, elevations, sections and perspectives of buildings Gibbs had designed and built. The quote is from his introduction, page i. A reprint is available from Dover Publications.
Part 1 of 2, the post for Gibb's design of the Menagery which was built is here: https://www.jgrarchitect.com/2021/12/james-gibbs-book-of-architecture.html
** I've posted about The Rule of Thirds in more detail here: