direct employment of the complicating operations.
I have thus sketched this line of thought in order to give you a rough notion of the kind of reasoning needed in this business. The reasoning which determined the first part of the rule is altogether too complicated to be explained orally. It would be easy enough to de scribe a way of getting rid of all the lines of identity in a graph while preserving its entire meaning. But the difficulty would be that in the case of a not excessively complicated graph, the different spots would run up into the thousands. But an overwhelming majority of them would be entirely useless. What is wanted is to join the junctures of corresponding [marks?] of all the different replicas of the same spot which occurs both within an odd