Page:Sir William Herschel, his life and works (1881).djvu/213

Rh his position was distinctly less advanced than that of. That great philosopher announced the true law governing the relation between the color and the thickness of the film. did not recognize such a relation. showed exactly how the phenomenon depended upon the obliquity at which it was viewed. found no place in his theory for this evident variation.

In the series of experiments described in the first paper on this subject, mistook the locus of a certain set of rings which he was observing. This mistake, though so slight as hardly to be detected without the guidance of the definite knowledge acquired in later times, not only vitiated the conclusion from the experiments, but gave an erroneous direction to the whole investigation. To him these experiments proved that conception of a periodic phenomenon was untenable. Thus cut loose from all hypothesis, his fertility in ideas and ingenuity in experimentation are as striking as ever. He tried the effect of having a polished