lying both in the same plain produc'd, may meet each other in any
assignable Angle; both which requisites may be very well perform'd by
the Engine describ'd in the third Figure of the first _Scheme_: where
AB signifies the Beam of a Lath fixt perpendicularly or Horizontally,
CD the two Poppet heads, fixt at about two foot distance, EF an Iron
_Mandril_, whose tapering neck F runs in an adapted tapering brass
Collar; the other end E runs on the point of a Screw G; in a convenient
place of this is fastned H a pully Wheel, and into the end of it, that
comes through the Poppet head C, is screwed a Ring of a hollow
_Cylinder_ K, or some other conveniently shap'd Tool, of what wideness
shall be thought most proper for the cize of Glasses, about which it is
to be imploy'd: As, for Object glasses, between twelve foot and an
hundred foot long, the Ring may be about six inches over, or indeed
somewhat more for those longer Glasses. It would be convenient also and
not very chargeable, to have four or five several Tools; as one for all
Glasses between an inch and a foot, one for all Glasses between a foot
and ten foot long, another for all between ten and an hundred, a fourth
for all between a hundred and a thousand foot long; and if Curiosity
shall ever proceed so far, one for all lengths between a thousand and
ten thousand foot long; for indeed the principle is such, that
supposing the _Mandrils_ well made, and of a good length, and supposing
great care be used in working and polishing them, I see no reason, but
that a Glass of a thousand, nay of ten thousand foot long, may be as
well made as one of ten; for the reason is the same, supposing the
_Mandrils_ and Tools be made sufficiently strong, so that they cannot
bend; and supposing the Glass, out of which they are wrought, be
capable of so great a regularity in its parts as to refraction: this
hollow _Cylinder_ K is to contain the Sand, and by being drove round
very quick to and fro by means of a small Wheel, which may be mov'd
with ones foot, serves to grind the Glass: The other _Mandril_ is