The mean fibre length, mean fibre diameter, mean fibre crimp ratio (i.e. ratio of length of the fibre under 2·5 mg. load to its length stretched), and a quantity approximately proportional to the ultimate tensile fibre strength, have been measured for twenty-five skirted Merino fleeces clipped from sheep that had been grazed at Robe (South Australia) on copperdeficient land and fed by mouth with amounts of copper varying from zero to 100 mg./day. Sulphur analyses and qualitative amino-acid analyses were carried out on some of the fleeces. The fleeces were processed one by one on the worsted system into yarn. The results show an increase in fibre diameter, an increase in ultimate tensile strength and an improvement in behaviour in processing with increasing dietary supplement of copper.

A contribution to these experiments through special skill or knowledge has been made by almost everyone on the staff at Torridon, and especially by the late W. L. Semple, J. G. Martindale and H. Beevers. Thanks are due to Messrs Isaac Holden and Sons Ltd. for their generous co-operation in carrying out part of the work at their mill and to Mr A. Prescott, Mr F. Sharp and Mr G. W. Owen of the Wool Control, and Mr F. R. Emmett of Messrs Laycock, Son and Co. Ltd., for their assistance in judging tops. The author would like to thank Mr B. H. Wilsdon, the Director of Research, for suggestions and encouragement during this work, and the Council of the Wool Industries Research Association for permission to publish this paper.