Ball, W. W. Rouse (Walter William Rouse), 1850-1925 · London, Macmillan · leaf 76
tical map-makers for a long time previously. ThroughDe Morgan the proposition then became generally known; andin 1878 Cayley* recalled attention to it by stating that he couldnot obtain any rigorous proof of it. Probably the following argument, though not a formaldemonstration, will satisfy the… … ABC or wholly inside the internal boundary, that is, it mustoccupy a position either like X or like X\ In either casethere is no possible way of drawing another area Y whicli shallbe contiguous with A,B,G, and X. In other words, it is possibleto draw on a plane four areas which are contiguous, but…
Geometry · Cryptography · Ciphers
Internet Archive · Wellesley College Library · Public Domain Mark 1.0. Free to use for anything.
