Circumscribing and Excising

Let C(n s) be a naphthalenic single coronoid, and apply the same notation for its circumscribed and excised systems as well as their invariants as in Sect. 5.4.6. Then the transformation (4.13) applied to eqns. (26) and (30) gives straightforwardly... 

Firstly, if an excised coronoid Cq, viz. c(Cq), is not itself a coronoid, then the circumscribing of c(Cq) is not defined, and Cq becomes automatically a core coronoid. The two last systems of the top and bottom rows of Fig. 4.2 (viz. C32H16 and C48H20) examples. In particular, every catacondensed coronoid is a core coronoid belonging to the category under consideration. If Q is a catacondensed single coronoid vdthout an inside feature (cf. Vol. I), then e(Q) consists of the inner perimeter of Q. 

It is clear that Cq is a core coronoid if the conditions of Observation 5.3 are fulfilled. But also, if a coronoid C has no fusing edge and e(C) is a coronoid, it is inferred that C is restored by circumscribing c(C) one only has to recall the mechanism of excising and circumscribing. 

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