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PART of the ensfuing Dif - courfe about ligbt was written at the defire of fome Gentlemen of the Royal So- ciety , IN the Tear 1675, and then fent to tbeir Secretary ,

 and read at their Meetings, and the reft was added about tweloe Tears after to complete the Tbeory;  ex- cept the tbird book,  and the left Propofition of the Second , which were fince put together out of fcatter'd Papers. To auoid be- ing engaged in Difputes about thefe !!!....