Page 404 - 89 history of astronomy_opt
P. 404

But the defects of colour remained, al-
                                         though their cause was unknown until New-
                                         ton carried out his experiments on disper-
                                         sion and the solar spectrum. To overcome
                                         the spherical aberration James Gregory,[2]
                                         of Aberdeen and Edinburgh, in 1663, in his
                                          Optica Promota , proposed a reflecting specu-
                                         lum of parabolic form. But it was New-
                                         ton, about 1666, who first made a reflecting
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