This block also
passes through a slot in D E, an arm at right angles to B C. A little
consideration will show that P', if worked at all, would trace out the
sum curve of P.
It was only when I showed the rough idea of this to Professor
Kennedy, with the view of ascertaining what would be the amount of
back-lash and friction, that I learned that Mr. Boys had already
invented a very similar integrator. In his model the double parallel
ruler is replaced by two endless strings and pulleys, and the bar, B
C, by a T square.
Although this integrator was afterward made in a less crude form, I do
not think it has ever been a practical instrument for the draughtsman.
Shortly afterward I came across a work by Abdank-Abakanowicz, entitled
"Les Integraphes," being a study of a "new kind of mechanical
integrator."
The new kind of integrator was really only an independent version of
Boys' instrument, but in many respects a great improvement. The real
merit will ultimately belong to the scientific instrument maker who
constructs an instrument reasonably cheap and capable of efficient
practical service. Abdank-Abakanowicz's integrator however certainly
went further in the practical direction than any previously
constructed.
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