March 26, 1965

Professor Elbert G. Smith
Department of Chemistry
Mills College

Oakland 13, California

Dear Professor Smith:

Many thanks for the elaboration on "Rule 30",

I am afraid it now eludes my purpose, to attempt a topological interpretation
of Wiswesser's original conjecture of a simple choice of initial locant.
(Simplicity is not always to be found in cyelic graphs!!)

Has there been a concerted effort to program a code - interpreter, i.e., a
system to convert linear code input into some abstract form for computation,

such as an ineidence matrix?

You may be amused at an example of graphic display output from a first-stage
DENDRAL interpreter program.

Would you care to see our computational system sometime? Actually, I am
planning a demonstration for Monday afternoon, April 19, when, it happens,
Dr. E. Garfield will be visiting.

a
Sincerely yours,

Joshua Lederberg
Professor of Genetics

P.S. As a matter of topological theory, does new Rule 43 allow a choice

between the isomorphs 10ALA vs. lOAMB of the attached figure?

Encl.: Topological mapping of organic molecules. Proc. Nat. Acad. Sei.
53:134-139.