The Practical Geometry of Boston's Old North Church

 

The Old North Church, in Boston's North End, was built in 1723.*

The church fathers responsible for its construction had visited England where they had probably seen the churches in London built after the Great Fire in 1669. Those churches were built using the new Classic architectural style which included half circle windows as are in the church instead of pointed ones.

I visit the church when I share/explore Practical Geometry with the North Bennet Street School Preservation Carpentry students. We, along with the instructors, see its construction first hand, from the crypt with its tombs to the timber roof frame in the attic.    

 This year I explored the church's geometry. The Historic Structures Report for the church, written c. 1950, includes floor plans which trace the evolution of the church interior. These are not HABS drawings, not as detailed and possibly not as accurate. This is, therefore, a preliminary exploration.

The exterior is brick. The floors and and roof are timber framed. One of the church fathers seems to have overseen the master mason responsible for the foundation and walls. A master timber framer was responsible for the roof. All of these men would have known Practical Geometry. 

 

 

Drawing #1 shows the church interior layout in 1730. The entrance and apse are extensions of the main space. The pulpit with its curvy stair is drawn to the left of the apse. In later years the pew locations, the stairs and some exterior doors change. 

The geometry of the exterior walls is simple. It is the 3/4/5 rectangle. The 2 3/4/5 triangles and the rectangle are outlined in red.

 

 

 

 

 

In Drawing #2 the black diagonals of the Rule of Thirds cross the interior. Where they cross are the points*** which locate the red vertical lines which divide the space in thirds. These lines layout the inside width of  the apse and the entry.  

The distance of 2 of the columns from the back and/or the front walls is also set: see the dashed red line at the 2/3-1/3 division of the church interior.

The apse plan is a half circle. The entry is square. Both are drawn in red. The  church wall is a little thicker at the entry to support the steeple. 

Drawing #3:  The square laid out by the Rule of Thirds ( in Drawing #2) can also be divided horizontally by the same Rule - see the black lines . The points allow 3 equal divisions across the church - the red lines, labeled A. 

 

 

 

 

   

Drawing #4: By adding  the Rule of Thirds' vertical lines  - again the black lines - the points are found on the red lines (A). These points locate the columns on both sides of the body of the church: the vertical red line which crosses the A lines at B to mark the distance between the 3 columns on each side along the length of the church. The fourth column, located in the space at the bottom of the drawing, uses the same spacing as .the other columns

 I have drawn only the left side. The right side matches the left. Too many lines become visually confusion.

 

Drawing #5: The windows were centered between the columns. 

In a time where candles and  torches were the only artificial lighting available, placing the windows for maximum natural light was essential.   

The arcs in black  on the right side locate the center line (C) of the window. 

The centers of radii for the arcs begin at the columns. IE: place your compass point on the outside edge of the column; swing an arc. Swing a similar arc from the opposite column. The line drawn by the 2 points where the arcs cross will locate the center of a window. 

*The church is best known for its steeple where Paul Revere hug his lanterns on April 15, 1775, warning the citizens of Massachusetts Bay by which route the British soldiers would march to Lexington and Concord.

 **This drawing is by Suzanne Carlson, from  John Fitzhugh Millar's book, The Architects of the American Colonies, Barre Publishers, Barre, MA, 1968. Used with permission from John Fitzhugh Millar.  

*** Remember that in geometry, Practical or otherwise,  a Line cannot be drawn without 2 points. To learn about the Rule of Thirds, see  https://www.jgrarchitect.com/2020/08/lesson-6-rule-of-thirds-part-1_21.html