A quote from "Four Colours Suffice" :
" Throughout the first half of 1976, Appel and Haken worked on the final details of the discharging procedure that would give them their unavoidable set of reducible configurations. To do this, they sought out problem configurations that would necessitate further changes to the discharging procedure. Whenever they found such a configuration, they immediately tested it for reducibility - which could usually be done fairly quickly - and in this way, the reducibility testing by computer could keep pace with the manual construction of the discharging procedure. In the event. the final process used 487 discharging rules, requiring the investigation by hand of about ten thousand neighbourhoods of countries with positive charge, and the reducibility testing of computer of some two thousand configurations. "
While reading the above par it occured to me that prior to reading the 200 odd pages leading up to it - the text would have seemed complete gibberish. Such are maths texts, piling definition upon definition often coming up with something rather beautiful.
I enjoyed this