Referring to the illustration of Felt’s first metal machine, it will be
noted that the machine has been partly dismantled. The model was robbed
of some of its parts to be used as samples for the manufacture of a
lot of machines that were made later. In view of the fact that this
machine is the first operative multiple-order key-driven calculating
machine made, it seems a shame that it had to be so dismantled; but the
remaining orders are operative and serve well to demonstrate the claims
held for it.
[Sidenote: _Felt patent 371,496_]
The mechanism of the machine is illustrated in the reproduction of the
drawings of Felt’s patent, 371,496, on page 58. The specification of
this patent shows that it was applied for in March, 1887, and issued
October 11, 1887.
From the outward appearance of the machine it has the same general
scheme of formation as is disclosed in the wooden model.
[Illustration: The First “Comptometer”]
[Illustration]
[Illustration: From Drawings of Felt Patent No. 371,496]
[Sidenote: _Description of Felt calculator_]
The constructional scheme of the mechanism consists of a series of
numeral wheels, marked A in the patent drawings. Each wheel is provided
with a ratchet wheel, and co-acting with the ratchet is a pawl mounted
on a disc E², carried by the pinion E¹, which is rotatably mounted on
the same axis as the numeral wheel. The arrangement of these parts is
such that a rotating motion given any of the pinions E¹, in a clockwise
direction, as shown in the drawings, would give a like action to
their respective numeral wheels; but any motion of the pinions in an
anti-clockwise direction would have no effect on the numeral wheels,
owing to back-stop pawls K, and stop-pins T, provided to allow movement
of the numeral wheels in but one direction.
Co-acting with each pinion E¹, is shown a long lever D, pivoted at
the rear of the machine and provided with a segmental gear rack which
meshes with the teeth of the pinion E¹. This lever comes under what is
now generally termed a segment lever.
Each lever is provided with a spring S, which normally holds the front
or rack end upward in the position shown in Fig. 1, and has co-acting
with it a series of nine depressable keys which protrude through the
casing and contact with the upper edge of the lever.
The arrangement of the keys with their segment levers provides that the
depression of any key will depress the segment lever of that order,
which in turn will rotate the pinion E¹ and its numeral wheel.
While this arrangement is such that each key of a series gives a
different degree of leverage action to the segment lever, and in
turn a degree of rotation to the numeral wheel of the same order in
accordance with the numerical value of the key depressed, it may be
conceived that the momentum set up by the quick stroke of a key would
set the numeral wheel spinning perhaps two or three revolutions, or at
any rate way beyond the point it should stop at to register correctly.
To preserve correct actuation of the mechanism and overcome its
momentum, Felt provided a detent toothed lever for each numeral wheel,
which will be found marked J¹ in the drawings. To this lever he linked
another lever G, which extended below the keys, and arranged the length
of the key-stems so that when each key had revolved the numeral wheel
the proper distance, the key will have engaged the lever G, and through
the link connection will have caused the detent tooth of the lever J¹
to engage one of the pins T, of the numeral wheel, thus bringing the
numeral wheel and the whole train of mechanism to a dead stop.
This combination was timed so that the (1) key would add one, the (2)
key would add two, etc., up to nine for the (9) key. Thus the prime
actuation of each wheel was made safe and positive.
[Sidenote: _Recapitulation of Art prior to Felt calculator_]
Before explaining the means by which the carry of the tens was effected
in the Felt machine without interfering with multiple-order prime
actuation, it will perhaps help the reader to recapitulate on what the
Art already offered.
Going back to the Art, prior to Felt’s invention, there are a few
facts worth reconsidering that point to the broadly new contributions
presented in the Felt invention, and combining these facts with a
little theory may perhaps give a clearer understanding of what was put
into practice.
In most lines of mechanical engineering in the past, the term “theory”
connected with mechanical construction was a bugaboo. But the solution
of the modern calculating machine was wholly dependent upon it.
Let us summarize on the Art, prior to Felt’s invention. A calculating
machine that would calculate, if we eliminate the key-driven feature,
was old. The key-driven feature applied to adding mechanism was old as
adapted to a single-order machine with a capacity for adding only a
single column of digits.
[Sidenote: _Why Hill failed to produce an operative machine_]
Hill attempted to make a multiple order key-driven machine, but failed
because he did not theorize on the necessities involved in the physical
laws of mechanics.
Hill saw only the columnar arrangement of the ordinal division of the
keyboard, and his thought did not pass beyond such relation of the
keys for conveyance. There is no desire to belittle this feature, but
it did not solve the problem that was set forth in the specification
and claims of his patent; neither did it solve it for anyone else who
wished to undertake the making of such a machine.
[Sidenote: _Idiosyncrasies of force and motion increased by use of
keys_]
The introduction of keys as a driving feature in the calculating
machine Art demanded design and construction suitable to control the
new idiosyncrasies of force and motion injected into the Art by their
use, of which the elements of inertia and momentum were the most
troublesome.
[Sidenote: _Light construction a feature_]
Hill, in the design and construction of his machine, ignored these two
elementary features of mechanics and paid the penalty by defeat. The
tremendous speed transmitted to the parts of a key-driven machine,
which has already been illustrated, required that lightness in
construction which is absolutely necessary to reduce inertia to a
minimum, should be observed. The Hill machine design is absolutely
lacking in such thought. The diameter of the numeral wheel and
its heavy construction alone show this. Lightness of construction
also enters into the control of momentum when the mechanism must
suddenly be brought to a dead stop in its lightning-speed action. A
heavily-constructed numeral wheel like that shown in the Hill patent
would be as hard to check as it would to start, even if Hill had
provided means for checking it.
Strength of design and construction, without the usual increase in
weight to attain such end, but above all, the absolute control of
momentum, were features that had to be worked out.
Robjohn partly recognized these features, but he limited the
application of such reasoning to the prime actuation of a single order,
and made nothing operable in a multiple key-driven machine.
Spalding and Bouchet recognized that the application of control was
necessary for both prime actuation and carrying, but, like Robjohn,
they devised nothing that would operate with a series of keys beyond a
single order.
[Sidenote: _Operative features necessary_]
An operative principle for control under prime actuation was perhaps
present in some of the single-order key-driven machines, but whatever
existed was applied to machines with keys arranged in the bank form
of construction, and, to be used with the keys in columnar formation,
required at least a new constructive type of invention. But none of
the means of control for carrying, prior to Felt’s invention, held any
feature that would solve the problem in a multiple-order machine.
[Sidenote: _Classification of the features contained in the early Art
of key-driven machines_]
While all the machines referred to have not been illustrated and
described here, fair samples of the type that have any pertinence
to the Art have been discussed, and those not illustrated would add
nothing more than has been shown. A classification of the inventions
referred to may be made as follows:
Parmelee and Stetner had no carrying mechanism; Hill, Robjohn,
Borland and Hoffman, Swem, Lindholm and Smith had no control for the
carry. Carroll, Bouchet and Spalding show a control for the carrying
action, which in itself would defeat the use of a higher wheel for
prime actuation, and which obviously would also defeat its use in a
multiple-order key-driven machine.
One of the principal reasons why theory was necessary to solve the
problem of the key-driven calculator existed in the impossibility
of seeing what took place in the action of the mechanism under the
lightning speed which it receives in operation. Almost any old device
could be made to operate if moved slow enough to see and study its
action; but the same mechanism that would operate under slow action
would not operate correctly under the lightning-speed action they
could receive from key depression. Only theoretical reasoning could be
used to analyze the cause when key-driven mechanism failed to operate
correctly.
[Sidenote: _Carrying mechanism of Felt’s calculator_]
Referring again to the drawings of the Felt patent, which illustrate
the first embodiment of a multiple-order key-driven calculating
machine, we find, what Felt calls in the claims and specifications,
a carrying mechanism for a multiple-order key-driven calculating
machine. This mechanism was, as set forth in the specification, a
mechanism for transferring the tens, which have been accumulated by
one order, to a higher order, by adding one to the wheel of higher
order for each accumulation of ten by the lower order wheel. This, in
the Felt machine, as in most machines, was effected by the rotation of
a numbered drum, called the numeral wheel, marked with the nine digits
and cipher.
[Sidenote: _Transfer devices_]
The term “transfer device” for such mechanism was in common use, and as
a term it fits certain parts of all classes of devices used for that
purpose, whether for a crank-driven, key-driven, or any other type
of multiple-order or single-order machine. But in the Felt invention
we find it was not the simple device generally used for transferring
the tens. It was, in fact, a combination of devices co-acting with
each other which, in the specification of the patent, was termed the
carrying mechanism.
[Sidenote: _Carrying mechanism versus mere transfer devices_]
Now, carrying mechanism may in a sense be termed a transfer device,
as one of its functions is that of transferring power to carry the
tens, but a mere transfer device may not be truthfully termed a
carrying mechanism for a multiple-order key-driven machine unless it
performs the functions that go to make up a correct carrying of the
tens in that class of machine, and which we find laid down under the
head of carrying mechanism in the Felt patents, where we find the
first operative carrying mechanism ever invented for a multiple-order
key-driven machine.
The functions demanded of such a piece of mechanism are as follows:
First, the storing of power to perform the carry; second, the
unlocking of the numeral wheel to be carried; third, the delivery
of the power stored to perform such carry; fourth, the stopping and
locking of the carried wheel when it has been moved to register such
carry; and fifth, clearing the carrying-lock during prime actuation. A
seemingly simple operation, but let those who have tried to construct
such mechanism judge; they at least have some idea of it and they will
no doubt bow their heads in acknowledgment of the difficulties involved
in this accomplishment.
Mechanism for carrying the tens in single digit adders was one thing,
and such as was used could well be called a transfer device; but
mechanism for carrying the tens in a real key-driven calculating
machine was another thing, and a feature not solved until Felt
solved it, and justly called such combination of devices a “carrying
mechanism.”
[Sidenote: _Details of Felt carrying mechanism_]
In the Felt machine, the carrying mechanism consisted of a lever and
ratchet pawl action, constructed of the parts M, m², operated by a
spring m, the pawl acting upon the numeral wheel pins T, to ratchet
the wheel forward under the spring power. The power in the spring was
developed from the rotation of the lower wheel, which through the means
of an envolute cam[2] attached to left side of each wheel, operated
the carrying lever in the opposite direction to that in which it was
operated by the spring. As the carrying lever passed the highest point
of the cam spiral and dropped off, the stored power in the spring
retracted the lever M, and the pawl m², acting on the higher order
wheel pins T, and moved it one-tenth of a revolution.
[2] NOTE: As all the drawings of the Felt patent are not reproduced
here, the cam is not shown.
This part of the mechanism was in principle an old and commonly-used
device for a one-step ratchet motion used in the carry of the tens.
It served as a means of storing and transferring power from the lower
wheel to actuate the higher wheel in a carrying operation, but a wholly
unqualified action without control.
In the Felt machine a spring-actuated lever N, mounted on the same axis
with the carrying lever, and provided with a detent stop-hook at its
upper end, served to engage the numeral wheel at the end of its carried
action, and normally hold it locked.
An arm or pin P, fixed in and extending from the left side of the
carrying lever and through a hole in the detent lever, acted to
withdraw the detent lever from its locking engagement with the numeral
wheel as the carrying lever reached the extreme point of retraction;
thus the wheel to be carried was unlocked.
Pivoted to the side of the detent lever is a catch O. This catch
or latch is so arranged as to hook on to a cross-rod q, especially
constructed to co-act with the catch and hold the detent lever against
immediate relocking of the numeral wheel as the carrying lever and pawl
act in a carrying motion. The latch has a tail or arm p, which co-acts
with the pin P on the carrying lever in such a way as to release the
latch as the carrying lever finishes its carrying function.
Thus the detent lever N is again free to engage one of the control
or stop-pins T to stop and lock the carried numeral wheel when the
carrying lever and pawl, through the action of the spring stored in the
carrying, has moved the wheel the proper distance.
[Illustration: Bill for First Manufacturing Tools of the “Comptometer”]
A lot of functions to take place in ¹/₁₆₅ of a second, but it worked.
The timing of the stop and locking detents, of course, was one of the
finest features.
[Illustration: Early Comptometer]
The normal engagement of the carrying detent, it may be understood,
would prevent the movement of the wheel by key action or prime
actuation, but the patent shows how Felt overcame this.
The carrying stop and locking detent lever N is provided with a cam-arm
or pin N, which was arranged to co-act with the cam disc E (see Fig.
1), fast to the prime actuating pinion E. The cam surface was short
and performed its function during a short lost motion arranged to take
place before the ratchet pawl would pick up and move the numeral wheel
under key actuation.
The camming action was outward and away from the center, and thus
released the carrying stop from its locking position with the numeral
wheel, and continued rotation of the pinion and cam disc would hold the
lock out of action until the parts had returned to normal.
With the return action of the keys, segment lever, pinion and cam disc,
through the action of a spring attached to the segment lever, the
carrying stop detent will again engage and lock the numeral wheel.
[Sidenote: _Manufacture of the Felt calculator_]
Felt really started to manufacture his calculating machine in the fall
of 1886, after perfecting his invention. Having only a very limited
amount of money with which to produce machines, young Felt, then but
24 years of age, was obliged to make the machines himself, but with
the aid of some dies which he had made for some of the principal parts
(see reproduction of bill for dies on opposite page), he was able
to produce eight finished machines before September, 1887. Two of
these machines were immediately put into service, for the training of
operators, as soon as they were finished.
[Sidenote: _Trade name of Felt calculator_]
Of the first trained operators to operate these machines, which were
given the trademark name “Comptometer,” one was Geo. D. Mackay, and
another was Geo. W. Martin. After three or four months’ practice Mr.
Martin demonstrated one of these machines to such firms as Sprague,
Warner & Co., Pitkin & Brooks, The Chicago Daily News, and the Chicago,
Burlington & Quincy R. R. Co., and finally took employment with the
Equitable Gas Light & Fuel Co. of Chicago (see letter on opposite page)
as operator of the “Comptometer.” The Gas Co. has since been merged
with several other companies into the Peoples Gas Light & Coke Co. of
Chicago.
A very high testimonial of the qualities of the Felt invention was
given by Mr. Martin in 1888, a year after he entered the employment of
the Gas Co., and is reproduced on page 72.
Another fine testimonial was given by Geo. A. Yulle, Secy. & Treas. of
the Chicago Gas Light & Coke Co., in September, 1888 (see page 74). Mr.
Mackay, the other operator, secured employment with Albert Dickinson &
Co., Seed Merchants, as operator of the “Comptometer.” Mr. Mackay was
interviewed a few months ago, and was at that time, after thirty years,
still with the same firm, and a strong advocate of the “Comptometer.”
[Illustration: Letter from Geo. W. Martin]
[Illustration: Testimonial]
[Illustration: Testimonial]
[Illustration]
[Illustration: Letters from Elliott and Rosecrans]
[Sidenote: _Felt calculator Exhibit at National Museum_]
In September, 1887, Felt took one of the first eight machines to
Washington and exhibited it to Gen. W. S. Rosecrans, then Registrar of
the Treasury, and left the machine in the office of Dr. E. B. Elliott,
Actuary of the Treasury, where it was put into constant use. Proof of
the date of this use of Felt’s invention in the Treasury is set forth
in the reproduction of two letters (see opposite page), one was written
by Mr. Elliott and another by Gen. W. S. Rosecrans, in answer to an
inquiry of the Hall Typewriter Co. of Salem, Mass. Another of the first
eight machines was placed with Dr. Daniel Draper, of the N. Y. State
Weather Bureau, New York City.
Felt finally closed a deal with Mr. Robert Tarrant of Chicago, whereby
a partnership contract was signed November 28, 1887. The partnership
was incorporated January 25, 1889, under the name of the Felt & Tarrant
Mfg. Co., who are still manufacturing and selling “Comptometers” under
that name.
[Sidenote: _Significant proof of Felt’s claim of priority_]
Laying aside all the evidence set forth in the foregoing history of
key-driven machines and their idiosyncrasies, significant proof of
Felt’s claim as the first inventor of the modern calculating machine
is justified by the fact that no other multiple-order key-driven
calculating machine was placed on the market prior to 1902.
Lest we lose sight of a most important feature in dealing with the Art
of the Modern Calculator, we should call to mind the fact that as Felt
was the originator of this type of machine, he was also the originator
of the scheme of operation in its performance of the many and varied
short cuts in arithmetical calculation.
The performance of calculation on machines of the older Art differed so
entirely from the new that any scheme of operation that may have been
devised for their use would lend nothing to the derivation of the new
process for operating the key-driven machine of the new Art.
[Sidenote: _Rules for operation an important factor of modern
calculator_]
A superficial examination of one of the instruction books of the
“Comptometer” will convince most any one that it is not only the
mechanism of the machine that made the modern calculator so valuable
to the business world, but also the schemes laid down for its use. The
instructions for figuring Multiplication, Subtraction, Division, Square
Root, Cube Root, Interest, Exchange, Discount, English Currency, etc.,
involved hard study to devise such simple methods and rules.
The instruction books written by Felt for the “Comptometer, the Modern
Calculator,” reflect the genius disclosed in the invention of the
machine itself.
[Illustration]
[Illustration]
[Illustration: From Drawings of Barbour Patent No. 133,188]