vi ACKNOWLEDGEMENTS
willingly of their valuable hours ; and to the Delegates and staff
of the Oxford Press, I would here tender my grateful thanks.
My debt to Professors F. W. Taussig and Viner will be sufficiently
 obvious in the text.
I owe a special tribute to Professor D. B. Copland, whose
interest and criticism were my greatest stimulus; to Mr. C. H.
Wickens, Commonwealth Statistician, who was always ready
to produce and interpret statistics; and. to Mr. Keith Isles,
whose criticism and help in reading proofs were invaluable.
G.L. W.

UNIVERSITY OF MELBOURNE,
January, 1930.