2 Of the many frustrations of any editor, surely, avoidable delay is the greatest. And this frustration is almost infinitely compounded when in the interim an unexpected death occurs. Professor Ferguson sent this manuscript as a draft; certain questions which he raised in the accompanying letter would normally have been resolved in the exchange of two or three letters or 'phone calls. I placed one call to learn he was ill; rather than press the query, I delayed. When next I 'phoned, I was shocked to learn of his completely unexpected and therefore all the more untimely death. Because the draft he sent contains so much of his own style and vigor, I have elected to print it in this incomplete form. The points he raised in his letter remain unclarified. In the face of this series of events, I have asked Professor Nell to undertake the task initially given to Ferguson. The two rarely saw things in the same way. Thus, the choice of Nell was not intended to finish Ferguson's incomplete assessment. I mention the foregoing simply to explain the unique treatment in these review essays. Of Charles Ferguson's death so little can be said-he was an ebullient souil, and a man of significant originality. -M. P.

I. Introduction, 465. — II. A neoclassical model of growth, 465. — III. The variable natural rate of growth, 466. — IV. Analysis of the variable path, 468. — V. Conclusion, 471.

I. Introduction, 79. — II. Expectations and conventional models of growth, 82. — III. A linear, variable accelerator, 87. — IV. Simple models of growth with variable accelerator, 90. — V. Conclusions, 92. — VI. Mathematical analysis, 95.

C. E. Ferguson, Cross-Section Production Functions and the Elasticity of Substitution in American Manufacturing Industry, The Review of Economics and Statistics, Vol. 45, No. 3 (Aug., 1963), pp. 305-313