The Felt Calculating Machine
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.
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.
The First “Comptometer”
From Drawings of Felt Patent No. 371,496
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.”
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.
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.
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.
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.
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.
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.”
Letter from Geo. W. Martin
Testimonial
Testimonial
Letters from Elliott and Rosecrans
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.
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.
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.
From Drawings of Barbour Patent No. 133,188
Early Efforts in the
Recording Machine Art
The Art of recording the addition of columns of figures is old in principle, but not in practice. Many attempts to make a machine that would record legibly under all conditions failed. These attempts have been pointed out from time to time as the first invention of the recording-adding machine, especially by those desirous of claiming the laurels.
First attempt to record arithmetical computation
The first attempt at arithmetical recording for which a patent was issued, was made by E. D. Barbour in 1872 ([see illustration on opposite page]).
E. D. Barbour has also the honor of being the first inventor to apply Napier’s principle to mechanism intended to automatically register the result of multiplying a number having several ordinal places by a single digit without mentally adding together the overlapping figures resulting from direct multiplication. He patented this machine in 1872 just prior to the issue of his arithmetical recorder patent. ([See page 181].)