Zurich, on conditions laid down by me, namely, that the cost should
not exceed £14, and that polar distances should range between one and
ten half-inches. The first machine made by Coradi on these lines was,
by a misunderstanding, sold in Germany, but the one I exhibit is the
first, I believe, that has reached England, and to this extent I may,
perhaps, be permitted to call it new. I look upon it rather as a
suggestion upon which a still more practical instrument can be made in
this country than as a perfect model. I believe there would be a wide
sale for such an instrument were it once generally known to exist,
and, what is more to work efficiently. It remains for me to point out
in what the Abdank-Abakanowicz, or, rather, Coradi, integraph differs
from Boys' instrument.

Two points deserve special attention. In the first place, the fixed
frame is abolished, and the horizontal motion of P (Fig. 3), the guide
point, is produced by putting the whole frame on friction rollers; in
the second place, as a necessary result of the first change, the guide
point carries about with it its own polar system, which renders the
changes in length of "rays" much more manageable. f f, f' f' is a
frame moving on four roughed wheels, e e e e, so that it can only move
in the direction, f', which we may term horizontal. f f and f' f' are
rails guiding the chariots, A and B, from f to f and from f' to f'. Of
these chariots, A contains the guide point, P, to trace out the
primitive with, and B the pencil, P', to draw the sum curve, i.e., the
tracer. The chariot, B, like Boys' tracer, is heavily loaded. g g is a
horizontal bar rigidly attached to the crossbars, q q and q' q', of
the frame. On g g is a movable pivot, to which h, which determines the
pole, k0 h being the polar distance. k0 is the position of a
second point, k, on the chariot, A, when the guide point, P, is on the
initial line, g g. l l is a bar with a long slot in it, in which work