JI~MAR~75 16:59:51,1155

Date: 31 MAR 1975 1659~PST

From: CARHART

Subject: WEATERVANES

To: LELERBERG

cc: CARHART

YES, I HAVE ACTUALLY BUILT MY 26-NODE STRUCTURE AND THE
GROUP IS CORRECT. THE WEATERVANES CAN BE FIT TOGETHER
BECAUSE THE TRIANGULAR PERIMETER HAS A PATTERN LIFE
(C.X.C.X.C.X.] - THAT IS, EACH EDGE OF THE TRIANGLE
READS C-X-C. THUS THERE IS NO CONFLICT IN

ASSEMBLING THEM. THE “HANDEDNESS" OF THE FACES
DERIVES NOT FROM TYE PERIMETER OF THE FACES

BUT FROM THE INTERNAL PORTION. IF THE TETRAHEDRON

IS DRAWN IN THE PLANAR REPRESENTATION, THEN

YOU CAN ORIENT THE FACES PROPERLY BY GIVING EACH

SMALL INNER TRIANGLE A CLOCKWISE ORIENTATION,

AND GIVING THE LARGE OUTER TRIANGLE A COUNTERCLOCKWISE
ORLENTATION. I SEE NOW WHAT THE SOURCE OF THE
CONFUSION MIGHT BE ~ I SAID THAT THE PINUHEELS

"PIGHT EACH OTHERS CURRENT” AT EVERY ENGE, BUT

I DIDN’T MEAN THAT THE HANDEDNESS WAS DIFFERENT.

IF THE TETRAHEDRON IS A SOLID OBJECT, EACH FACE

TS PAINTED WITH THE SAME HANDEDNESS. OF COURSE,

THIS IS EXACTLY THE IDEA YOU PRESENTED, EXCEPT

THAT THE CHIRALITY OF EACH NODE OF THE TETRAHEDRON
DERIVES FROM THE OPPOSING FACE.

RAY

wwe ee eee