APPLIED optics, once a languishing subject, has now largely emerged from the phase of semi-stagnation on one hand, and exploitation on the other, in which the outbreak of the Warfound it, and this book, contrasted with the predecessors of its class, emphasises the decided present-day trend of the science. In his endeavour to confine his attention to ‘real optics’, Prof. Conrady has been influenced by some well-known criticisms of Prof. Silvanus Thompson. What was known as ‘geometrical optics’ has, indeed, in more recent years, barely held its own against its critics, for it had certainly encroached to an unjustifiable extent upon neighbouring fields, at a period when unscrutinised criteria and false generalisations entered largely into its practical application. The optical designer, examining his problems by the aid of such imperfect theoretical means, saw as through a glass darkly, quite unperceiving the imperfect nature and inadequacy for his purposes of the methods currently adopted and the shadow of fact which they revealed. In later years the working of an ampler conception of the subject has removed the old inconsistencies and indicated fresh avenues of considerable possible development of the older plain theory.
Applied Optics and Optical Design.
By Prof. A. E. Conrady. Part 1. Pp. ix + 518. (London: Oxford University Press, 1929.) 50s. net.