equipment, and to Dr. G. E. R. Deacon and the a residue on each chain every 3.4 A. in the z-direc- captain and officers of R. R.S. Discovery II for their tion. We have assumed an angle of 36between part in making the observations. at residues in the same chain, so th he 1Young, F. B., Gerrard, H., and Jevons,., Phil Mag., 40, 149 structu on each chain, that