bid adieu to it eternally, excepting what I do for my private satisfaction, or leave to come out after me; for I see a man must either resolve to put out nothing new or to become a slave to defend it." It was fortunate that these disputes did not damp Newton's ardour as much as he feared. He later published many papers in the Philosophical Transactions on various aspects of optics, and, although some of his views are erroneous, and are now almost universally rejected, his investigations led to discoveries which are of permanent value. He succeeded in explaining the colour of thin and of thick plates (diffraction), and the inflexion of light, and he wrote on double refraction, light polarisation and binocular vision. He also invented a reflecting quadrant for observing the angles between the moon and the fixed stars— the same in every essential as the historically important navigational instrument more commonly known as Hadley's quadrant. This discovery was communicated by him to Edmund Halley in 1700 but was not published, or communicated to the Royal Society, until after Newton's death, when a description of it was found among his papers. Conflict over oratorship elections In March 1673 Newton took a prominent part in a dispute in the university. The public oratorship fell vacant, and a contest arose between the heads of the colleges and the members of the Senate as to the mode of electing to the office. The heads claimed the right of nominating two persons, one of whom was to be elected by the senate. The senate insisted that the proper mode was by an open election. George Villiers, 2nd Duke of Buckingham, who was the chancellor of the university, endeavoured to effect a compromise which, he says, "I hope may for the present satisfy both sides. I propose that the heads may for this time nominate and the body comply, yet interposing (if they think fit) a protestation concerning their plea that this election may not hereafter pass for a decisive precedent in prejudice of their claim", and, "whereas I understand that the whole university has chiefly consideration for Dr Henry Paman of St John's College and Mr. Craven of Trinity College, I do recommend them both to be nominated." The heads, however, nominated Drs Paman and Ralph Sanderson (of St John's); the next day 121 members of the senate recorded their votes for