UNIVERSITY OF CALIFORNIA

VIRUS LABORATORY
BERKELEY 4, CALIFORNIA

January 6, 1955

Dear Dostsr Franklin:

Dr. Rosalind Franklin Page 2 January 6, 1955

There remains the possibility that the rods have a slowly-turning

hexagonal contour, but that the corner-to-corner diameter of the
hexagon is 150 A, and the minor diameter is 130 A.
of Bernal and Fankuchen yield only the center-to-center separation of
the rods, and give no information about the actual diarneter of the
rods.  This would be a fine model, allowing a hexagonal cross-section
in any thin section, providing for space between the rods, and resulting
in a minimal center-to-centetr separation af 150 A,  The difficulty is
that the calculated density would not)'be entirely out of accord with
the observed value,

The observations

-

  So I am afraid this letter is of no use, except that it points
out the density difficulty in an assumed cylindrical model, and it
reiterates the fact that numerous hexagonal platelets have been
photogrz;lphed here, at Wisconsin, and at Y.I.T. I wish a consistent
contour could be found which would fit together the e~id8m(s from
X-ray analysis, birefringence, density determinations, and electron
microscopy.

With b6st regards and wiehes,

Sincerely,

Robby C.t Williams