CHRISTIAN HUYGENS AND THE DEVELOPMENT OF SCIENCE IN THE SEVENTEENTH CENTURY By A. E. BELL. PREFACE: THERE can be no doubt that Christian Huygens was one of the greatest scientific geniuses of all time. A man who transformed the telescope from being a toy into a powerful instrument of in vestigation, and this as a consequence of profound optical researches; who discovered Saturn's ring and the satellite Titan; who drew attention to the Nebula in Orion; who studied the prob lem of gravity in a quantitative manner, arriving at correct ideas about the effects of centrifugal force and the shape of the earth; who, in the great work Horologium Oscillatorium, founded the dynamics of systems and cleared up the whole subject of the compound pendulum and the tautochrone; who solved the out standing problems concerned with collision of elastic bodies and out of much intractable work developed the general notion of energy and work; who is rightly regarded as the founder of the wave theory in light, and thus of physical optics such a man deserves memory with the names of Galileo and Newton, and only the accidents of history have so far prevented this. It might be argued that Robert Hooke, who like Huygens was influenced by Descartes 's teachings, is of equal stature and showed as much inventive genius and intuition. In the extraordinary range of their activities there is some similarity. The overwhelming difference lies in the fact that Huygens was a great mathema tician and exponent of the quantitative method, whereas Hooke could never get beyond the first phase of a piece of work: that which led to the need of exact measurement and the discovery of mathematical relations. Having made this claim for Huygens, it is natural to ask how he compares with Newton. It is a question which arises from time to time in these pages, and one to which there is no epigrammatic answer. In some senses it was Huygens's greatest misfortune to grow up under the powerful influence of Descartes, who was a grfeat friend of his father, a frequent visitor to the family, and master of at least one disciple who taught Huygens at the university. From Descartes too many of Huygens's hypotheses were taken, so much so that he might stand as the exact opposite of Newton, whose objection hypotheses non fingo he did so much to call forth. Looking at Huygens in this way it is easy to dismiss him as a Cartesian, one whose ideas were largely superseded after the publication of Newton's Principia. But this would be a serious mistake. If he could not so brilliantly see the way to extend the sphere of natural law to the heavens, perceiving that the task of science is not to disclose a mechanism so much as to arrive at laws, he neverthe less did important work to prepare men of science for this modern attitude. If Newton owed nothing to Huygens, and he certainly owed exceedingly little, it is very probable that he was indebted in another way, for it may well have been the feeling of dissatisfaction with the position men like Huygens were reaching that drove Newton to make the new instauration Bacon had looked for a renovation of natural philosophy. The progress of scientific explanation may then be seen to be a process of leaving out redundant elements, of emancipation from imaginary qualities, until one arrives at the really successful procedure of abstraction. But Huygens was in all other senses an astoriishingly modern thinker, and he had the disposition which sets out to face things as they are which marks the man of science as much as does the possession of specialized knowledge. As a scientific researcher he was the first of a new prof