I wanted a good one, not the flimsy kind I had in elementary school. I wanted to see and touch it, so buying it on-line was not an option. I am still looking for a bigger one.
So, now I am playing! This morning I added circles to the sketch of Lorenzo.
The results are interesting. The radius for the arc of the fan light over the door has its center in the center of the door. The circle encloses the entry as it did for the 1795 entrance I just rebuilt.
The same circle fits the curve over the windows that unites the pilasters. The ellipse is the same curve as the fanlight coming back upon itself.
I know I like this. It is so simple, so straightforward: no wonder the house feels so right! The elements reinforce the important places. The parts speaks to each other, they're related.
It's also how architects and contractors on the job actually work. Imagine the mason thinking about the arch he needs to build over the door. He makes a wood frame to set in the opening so he can lay up the bricks from one side to the other. (Once the bricks are mortared in place the frame is removed.) Then he needs to span the spaces above, which happen to be the same width. So, use the same frame - obvious!
In 1800, masons did not have stone lintels to use over door and window openings. The brick arch spanned the distance. Here the arch transferred the roof load to the brick pilasters, leaving much less weight to be carried over the windows - structurally a smart idea. The arch, which had to be there, was not hidden. It generated the graceful design that still resonated today - art and science intertwined.
I also know I am working with a drawing based on a photograph and the scale is about 1 inch= 10 feet. Lots of margin for error. Still, it does please me.