If the chariot, B, could be put upon f f and work, if needful,
by a double parallelogram from m m, we should have, excepting the skew
pull, some great practical advantages. We might throw the whole of the
weight of the machine on the one pair of friction wheels, and replace
the other pair by a single wheel, the portion q' f' f' q' of the
machine virtually disappearing. Three wheels, of course, would be a
real improvement. Further, we should have the sum curve and primitive
drawn to the same base line, and the simplification in the number of
parts ought largely to reduce the cost of the instrument.
To be able to perform "inverse summation" (which in the language of
differential calculus is to find y as a function of x, when we are
given y=f(dy/dx), and not dy/dx=f(x) as usual), we only want a means
of making the plane of the wheel, w, parallel instead of perpendicular
to m' m', and it is easy to design a modification in the construction
which will allow of this change.
I hope the above description of the integraph may have made its
construction and method of working sufficiently clear. Those of you
who have a taste for mechanical work, and the necessary tools, might,
I think, with some patience, construct a workable integraph.
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