"His main design seems to have been to explain only those parts off Newton's Philosophy which have been controverted: and this is supposed to be the reason why his grand discoveries concerning light and colours, are but transiently and generally touched upon; for it is known, that whenever the experiments, on which his doctrine of light and colours is foimded, had been repeated with due care, this doctrine had not been contested; while his accounting for the celestial motions, and the other great appearances of nature, from gravity, had been misunderstood, and even attempted to be ridiculed."