equal to AB. Through this long socket
slides a rod KP, the end P being formed into an eye, by which this rod is
pivoted to the block which slides in the long slot, and thus controls the
motion of the block; and the pivot at P is centrally drilled to carry the
pencil. It is thus apparent that the center line of the slot TT must in
all positions be tangent to the hyperbola PBR, which will be traced by
the pencil, whose motions are so restricted as always to satisfy the
conditions explained in connection with Fig. 2.

The apparatus as thus represented does not at first sight appear unduly
complicated. But in order to render it adjustable, so that hyperbolas of
varying eccentricities and on different scales may be drawn with it,
several parts not here shown must be added. A frame must be provided, in
which to arrange supports for the pivots at F and F', and these supports
connected by a right and left handed screw, or equivalent means of
altering the distance between the foci; the crank CI and the socket F'G
must be of variable length, and these in each case would require to be
carefully adjusted. So that, as we stated in the beginning, it is
questionable whether a draughtsman of ordinary skill could draw the curve
any more readily by the aid of such a piece of mechanism than he could
without it; but it may claim a passing notice as a novel device, and the
first one, we believe, for describing the hyperbola by a combination of
rigid parts.

* * * * *

EXPERIMENTS WITH FIBERS.

By Dr. THOMAS TAYLOR.

As Microscopist of the United States Department of Agriculture, I am
frequently called upon to make investigations as to the character of
textile fibers and fabrics, not only for the public generally, but also
for several departments of the Government.

Textile fibers are presented both in the raw and as articles of
manufacture. In the latter case they may have been dyed, stained, or
painted. It is obvious that under these conditions the fibers should be
subjected to chemical reaction to bring them as nearly as possible to
their normal condition.

Considering how well the structures of the common textile fibers of
commerce--cotton, flax, ramie, hemp, jute, Manila hemp, silk, and
wool--have been investigated and minutely described by able and exact
microscopists, I will in this paper confine myself chiefly to such
experiments as I have personally made with textile fibers, treating t