100 YEARS AGO
In the October issue of the American Naturalist, Prof. H. F. Osborn reconsiders the evidence in favour of the existence of a common ancestral stem from which have diverged dinosaurs and birds. It is argued that many of the resemblances between these groups are adaptive rather than genetic, while the apparent close correspondence in the structure of the pelvis between adult birds and the herbivorous dinosaurs (which are specialised types) is due in a considerable degree to a misinterpretation of the homology of some of their elements. Nevertheless, the resemblances between the two groups are so numerous as to justify the belief of kinship. And special importance attaches to the opinion that some sort of bipedalism was a common character of all dinosaurs, the suggestion being countenanced that certain forms, like Stegosaurus, have reverted from a bipedal to a quadrupedal mode of progression.
From Nature 22 November 1900.
50 YEARS AGO
To inquire into the early stages of development of a scientific theory is no idle curiosity. Indeed, no adequate appreciation of its present state is possible if the various aspects which have gained prominence in the course of time are not traced back to their roots. This is especially true for the quantum theory of atomic systems, which presents such unfamiliar features and has led to such far-reaching conceptions as Niels Bohr's idea of complementarity. The history of quantum mechanics is, in fact, particularly instructive as an illustration of the inherent logic of the growth of scientific ideas. At the same time, it is not lacking in dramatic surprise: it forcefully reminds us that a vigorous flight of imagination can sometimes unexpectedly quicken the pace of a more methodical progress. It would be futile to try to date the birth of quantum mechanics from a particular discovery, or to relate it to a particular name. . . Nevertheless, it is possible to point to one inspiring idea, which gave the whole development unfailing guidance: it is Bohr's principle of correspondence, or (as he prefers to call it) correspondence “argument”. . . The young physicists who nowadays solve wave-equations as a matter of routine are not always taught how essential the correspondence point of view remains for the physical interpretation of the new formalism. Still less can they realize how essential an instrument it has been in the pioneering period of elaboration of this theory.
From Nature 25 November 1950.