Note 11 — Chapter III
Reading edition
M. Biot, in his Life of Newton, has stated that Newton was preceded in the invention of the reflecting telescope by Gregory, but probably without knowing it. It is quite certain, however, that Newton was acquainted with Gregory’s invention, as appears from the following avowal of it. “When I first applied myself to try the effects of reflection, Mr. Gregory’s Optica Promota (printed in the year 1663) having fallen into my hands, where there is an instrument described with a hole in the midst of the object-glass, to transmit the light to an eye-glass placed behind it, I had thence an occasion of considering that sort of construction, and found their disadvantages so great, that I saw it necessary before I attempted any thing in the practice to alter the design of them, and place the eye-glass at the side of the tube rather than at the middle.”—Letter to Oldenburg, May 4th, 1672.