a Traveller; for, as the man moves from the house or tree, so the house or tree seems to move from the man; or like one that sails upon a Ship, who imagines that the Ship stands still, and the Land moves; when as yet it is the Man and the Ship that moves, and not the House, or Tree, or the Land; so when a Man turns round in a quick motion, or when his head is dizzie, he imagines the room or place, where he is, turns round. Wherefore it is the Inherent Perceptive motions in the Eye, and not the motions in the Looking-glass, which cause these effects. And as for several figures that are presented in one glass, it is absurd to imagine that so many several figures made by so many several motions should touch the eye; certainly this would make such a disturbance, if all figures were to enter or but to touch the eye, as the eye would not perceive any of them, at lead not distinctly; Wherefore it is most probable that the glass patterns out those figures, and the sensitive corporeal motions in the eye take again a pattern from those figures patterned out by the glass, and so make copies of copies; but the reason why several figures are presented in one glass in several places, is, that two perfect figures cannot be in one point, nor made by one motion, but by several corporeal motions. Concerning a Looking-glass, made in the form or shape of a Cylinder, why it represents the figure of an external object in an other shape and posture then the object is, the cause is the shape and form of the Glass, and not the patterning motions in the Glass. But this discourse belongs properly to the Opticks, wherefore I will leave it to those that are versed in that Art, to enquire and search more after the rational truth thereof. In the mean time, my opinion is, that though the object is the occasion of the figure presented in a Looking-glass, yet the figure is made by the motions of the glass or body that presents it, and that the figure of the glass perhaps may be patterned out as much by the motions of the object in its own substance, as the figure of the object is patterned out and presented by the motions of the glass in its own body or substance. And thus I conclude and rest, Madam, _Your Faithful Friend_ _and Servant._ XXVI. _MADAM,_