An attempt will also be made to fill in some of the gaps in the first volume. The thirteen men and women herein described are by no means all and not… - Lyndall Fownes Urwick

It is this detachment, this use of comparison, his faith in the possibility of applying scientific processes of thought to the organisation of industry, which constitute Babbage's unique contribution to the advancement of management. More than half a century before Taylor was to illuminate the same point, with far greater effect because he was a practising engineer, Babbage had stumbled on the underlying truth that there are general principles applicable to the manufacture of products by machinery, and that it is an understanding of these principles rather than the technical knowledge of how to make a particular article which is of the first importance.

If they (the ) had not been (aware of human problems involved) — and Taylor either failed to encounter, or to recognize the significance of, the early work in industrial psychology contributed by Walter Dill Scott, Hugo Munsterberg, and others — there was the amazing fact that one of them, Frank Bunker Gilbreth, happened to fall in love with a girl who was a psychologist by education, a teacher by profession, and a mother by vocation. I know of no occurrence in the whole history of human thought more worthy of the epithet "providential" than that fact. Here were three engineers — Taylor, Gantt, and Gilbreth — struggling to realize the wider implications of their technique, in travail with a "mental revolution," their great danger that they might not appreciate the difference between applying scientific thinking to material things and to human beings, and one of them married Lillian Moller, a woman who by training, by instinct, and by experience was deeply aware of human beings, the perfect mental complement in the work to which they had set their hands.

No superior can supervise directly the work of more than five or, at the most, six subordinates whose work interlocks. The reason for this is simple. What is supervised is not only the individuals, but the permutations and combinations of the relationships between them. And while the former increase in arithmetical progression with the addition of each fresh subordinate, the latter increase by geometrical progression. If a superior adds a sixth to five immediate subordinates he Increases his opportunity of delegation by 20 per cent, but he adds over 100 per cent to the number of relationships he has to take into account. Because ultimately it is based on the limitations imposed by the human span of attention, this principle is called The Span of Control.