I came across the following paper by Ahti Pietarinen: https://www.researchgate.net/publication/271419583_Two_Papers_on_Existential_Graphs_by_Charles_Peirce
In that article, Ahti includes and comments on two papers. The first is "a paper prepared and read for the National Academy of Sciences, Washington DC, 16–18 April 1906." In this one, he uses the notation I claimed was his final preferred notation: shading the negative areas and leaving the positive areas unshaded. In the second paper from 1911, Peirce also used shading for the negative areas and white for the positive areas. But he wrote "It is needless to say that the process of making a black surface with a diagram in white upon it is insufferably inconvenient. For that reason in practice one substitutes Fig. 9 or Fig. 10 in place of Fig. 8." This is further evidence that Peirce preferred shading for distinguishing negative areas. With computer graphics today, it's easy to generate the shading. But if you're drawing EGs by hand (on paper, blackboard, or whiteboard), Peirce recommended the version without shading. John
----------------------------- PEIRCE-L subscribers: Click on "Reply List" or "Reply All" to REPLY ON PEIRCE-L to this message. PEIRCE-L posts should go to [email protected] . To UNSUBSCRIBE, send a message not to PEIRCE-L but to [email protected] with the line "UNSubscribe PEIRCE-L" in the BODY of the message. More at http://www.cspeirce.com/peirce-l/peirce-l.htm .
