Only praise can be given to any book written by Sir Stewart Duke-Elder. His "The Practice of Refraction" is now in its seventh edition, which is proof enough of its worth. It is intended to be a practical and complete guide to the would-be refractionist, and this it is without burdening him with mathematical formulae and proof for every statement. For example, a short chapter is devoted to aniseikonia, but ends with the statement that the true significance of this condition is still to be determined. It is emphasized that refraction cannot be learned from textbooks and that it is "an art which requires painstaking practice." Because it is an art, it is personal and no two refractionists follow exactly the same techniques. For this reason, this reviewer would prefer to see references to more complete papers on various subjects (eg, on the use of the cross cylinder or on