holes,
which may be screw'd on to the underside of a broad Plate of Ivory, on the
other side of which is to be made the divided Ring or Circle, to which
divisions the pointing of the Hand or Index, which is moved by the
conjoin'd Beard, may shew all the _Minute_ variations of the Air.

There may be multitudes of other ways for contriving this small Instrument,
so as to produce this effect, which any one may, according to his peculiar
use, and the exigency of his present occasion, easily enough contrive and
take, on which I shall not therefore insist. The whole manner of making any
one of them is thus: Having your Box or frame AABB, fitly adapted for the
free passage of the Air through it, in the midst of the bottom BBB, you
must have a very small hole C, into which the lower end of the Beard is to
be fix'd, the upper end of which Beard ab, is to pass through a small hole
of a Plate, or top AA, if you make use onely of a single one, and on the
top of it e, is to be fix'd a small and very light _Index_ fg, made of a
very thin sliver of a Reed or Cane; but if you make use of two or more
Beards, they must be fix'd and bound together, either with a very fine
piece of Silk, or with a very small touch of hard Wax, or Glew, which is
better, and the _Index_ fg, is to be fix'd on the top of the second, third,
or fourth in the same manner as on the single one.

Now, because that in every of these contrivances, the _Index_ fg, will with
some temperatures of Air, move two, three, or more times round, which
without some other contrivance then this, will be difficult to distinguish,
therefore I thought of this Expedient: The _Index_ or _Hand_ fg, being
rais'd a pretty way above the surface of the Plate AA, fix in at a little
distance from the middle of it a small Pin h, so as almost to touch the
surface of the Plate AA, and then in any convenient place of the surface of
the Plate, fix a small Pin, on which put on a small piece of Paper, or thin
Past-board, Vellom, or Parchment, made of a convenient cize, and shap'd in
the manner of that in the Figure express'd by ik, so that having a
convenient number of teeth every turn or return of the Pin h, may move this
small indented Circle, a tooth forward or backwards, by which means the
teeth of the Circle, being mark'd, it will be thereby very easie to know
certainly, how much variation any change of weather will make upon the
small wreath'd body. In the making of this Secundary Circle of Ve