Mr. Isaac Newton's considerations upon part of a letter of Monsieur de Bercé priinted in the eight french memoire, concerning the cata drioptrical telescope, pretended to be improv'd adn refined by M. cassegrain

That the Reader may be enabled the better to Judge of the whole, by comparing together the contrivances both of Mr. Newton and Mr. Cassegrain; it will be necessary, to borrow from the said French Memoire what is there concerning them: which is as followes. I send you (saith M. de Bercé to the Publisher of the Memoire,) the Copy of the Letter, which M. Cassagrain hath written to me concerning the proportions of Sr. Samuel Morelands Trumpet.