While these single-digit adding machines have been used to illustrate
how the control, which was lacking in the Hill invention, had been
recognized by other inventors as a necessary requisite to the
key-drive, it should not be construed that such carrying control as had
been applied to their inventions was of a type that could be used in
the Hill machine or in any multiple-order key-driven machine. It was
thirty years after the first attempt to control a key-driven machine
was made before an operative multiple-order key-driven machine, with a
control that would prevent over-rotation, was finally invented.
[Sidenote: _Theory versus the concrete_]
Theoretically, it would seem that the only feature or element lacking
in the Art prior to 1886, to produce a real key-driven calculator was
means that would control the carrying and also leave the carried wheel
free for key actuation. It was, however, quite a different problem.
Theoretical functions may be patched together to make a theoretical
machine; but that is only theory and not the concrete.
[Sidenote: _All but one of the generic elements solved_]
To take fragmental parts of such machines as were disclosed in the Art
and patch them together into anything practical was impossible, even
if one had been familiar with the Art and could devise mechanism to
supply the new element. That is, leaving aside the broad or generic
theoretical elements, which today, from knowledge gained by later
inventions, serve the make-up of a key-driven calculator, there was
still lacking any concrete example or specific design of a whole
machine, as there was no such machine disclosed in the drawings of
patents, or any known mechanism which, if arranged in multiples, would
be operative as a practical machine even if mechanism to supply the new
element were to be added.
In other words, while it is conceded from our present knowledge that
all but one of the generic theoretical elements had been solved as
disclosed in the various before-named machines, it required the
application of these elements in a different way from anything before
disclosed; which in itself required a different concrete form of the
generic principles for the whole machine as well as a generic form of
invention covering the new theoretical element.
It may be easy to analyze that which exists, but quite a different
story to conceive that which did not exist. With reference to the Art,
however, the production of the new element is a feature that may be
credited without question. The concrete does not enter into it other
than as proof that a new feature has been created.
[Sidenote: _Originality of inventions_]
While the discussion of the Art from a scientific standpoint brings
together in after years what has been accomplished by different
inventors, it is doubtful whether any of these early inventors had
other knowledge than what may possibly have been obtained from seeing
one of the foreign-made crank-driven machines. All inventors work with
an idea obtained from some source, but on the whole few copy inventions
of others. When an Art is fully established, however, and machines
representing the Art are to be found on the market and the principal
features of such machines are portrayed in a later patent, it may
rightly be called a copy. To assume, however, that a novice has taken
the trouble to delve into the archives of the patent office and study
the scattered theoretical elements of the Art and supply a new element
to make a combination that is needed to produce a practical key-driven
calculator, is not a probable assumption. But allowing such assumption
were possible, it is evident that from anything that the Art disclosed
prior to 1887 it was not possible to solve the concrete production of a
key-driven calculator.
[Sidenote: _A conception which led to the final solution_]
In 1884, a young machinist, while running a planer, conceived an idea
from watching its ratchet feed motion, which was indirectly responsible
for the final solution of the multiple-order key-driven calculating
machine. The motion, which was like that to be found on all planing
machines, could be adjusted to ratchet one, two, three, four or more
teeth for a fine or coarse feed.
While there is nothing in such a motion that would in any way solve the
problem of the modern calculator, it was enough to excite the ambitions
of the man who did finally solve it. It is stated that the young man,
after months of thought, made a wooden model, which he finished early
in 1885. This model is extant, and is illustrated on the opposite page.
The inventor was Dorr E. Felt, who is well known in the calculating
machine Art as the manufacturer of the “Comptometer,” and in public
life as a keen student of economic and scientific subjects. The wooden
model, as will be noted, was crude, but it held the nucleus of the
machine to come.
[Illustration: “Macaroni Box” Model]
[Illustration: Dorr E. Felt]
Mr. Felt has given some interesting facts regarding his experience in
making the wooden model.
[Sidenote: _Evolution of an invention_]
He says: “Watching the planer-feed set me to scheming on ideas for
a machine to simplify the hard grind of the bookkeeper in his day’s
calculation of accounts.
“I realized that for a machine to hold any value to an accountant, it
must have greater capacity than the average expert accountant. Now I
knew that many accountants could mentally add four columns of figures
at a time, so I decided that I must beat that in designing my machine.
Therefore, I worked on the principle of duplicate denominational
orders that could be stretched to any capacity within reason. The plan
I finally settled on is displayed in what is generally known as the
“Macaroni Box” model. This crude model was made under rather adverse
circumstances.
“The construction of such a complicated machine from metal, as I had
schemed up, was not within my reach from a monetary standpoint, so I
decided to put my ideas into wood.
[Sidenote: _Trials of an inventor_]
“It was near Thanksgiving Day of 1884, and I decided to use the holiday
in the construction of the wooden model. I went to the grocer’s and
selected a box which seemed to me to be about the right size for the
casing. It was a macaroni box, so I have always called it the macaroni
box model. For keys I procured some meat skewers from the butcher
around the corner and some staples from a hardware store for the key
guides and an assortment of elastic bands to be used for springs. When
Thanksgiving day came I got up early and went to work with a few tools,
principally a jack knife.
“I soon discovered that there were some parts which would require
better tools than I had at hand for the purpose, and when night came I
found that the model I had expected to construct in a day was a long
way from being complete or in working order. I finally had some of the
parts made out of metal, and finished the model soon after New Year’s
day, 1885.”
[Sidenote: _The first “Comptometer”_]
By further experimenting the scheme of the wooden model was improved
upon, and Felt produced, in the fall of 1886, a finished practical
machine made of metal. This machine is illustrated on the opposite page.