To avoid the long and time-consuming laying out of a boat by ordinates and
abscissas, I have constructed a handy apparatus, by which it is possible
without much trouble to obtain the sections of a vessel graphically and
sufficiently accurate. The description of its construction is given with
reference to the accompanying cut. A is a wooden rod of rectangular
section, to which are adapted two brackets, a_{1} a_{2}, lined with India
rubber or leather; a_{1} is fixed to the wood, a_{2} is of metal, and, like
the movable block of a slide gauge, moves along A. In the same plane is a
second rod, perpendicular to A, and attached thereto, which is perforated
by a number of holes. A revolving pin, C, is adapted to pass through these
holes, to which a socket, D, is pivoted, C acting as its axis. To prevent
this pin from falling out, it is secured by a nut behind the rod. Through
the socket, D, runs a rod, E, which carries the guide point, s_{1}, and
pencil, s_{2}. Over s_{1} a rubber band is stretched, to prevent injury to
the varnish of the boat. Back of and to A and B a drawing board is
attached, over which a sheet of paper is stretched.

[Illustration: THE FRAME TRACER.]

The method of obtaining a section line is as follows: The rod, A, is placed
across the gunwale and perpendicular to the axis of the boat, and its
anterior vertical face is adjusted to each frame of the boat which it is
desired to reproduce. By means of the brackets, a_{1} and a_{2}, A is fixed
in place. The bolt, C, is now placed in the perforations already alluded
to, which are recognized as most available for producing the constructional
diagram. At the same time the position of the pencil point, s_{2}, must be
chosen for obtaining the best results.