The Early Key-Driven Art

M. Le Colonel D’Ocagne, Ingénieur des Ponts et Chaussées, Professeur à l’École des Ponts et Chaussées, Répétiteur à l’École Polytechnique, in his “Le Calcul simplifie,” a historical review of calculating devices and machines, refers to the key-driven machine as having first made its appearance in the Schilt machine of 1851, but that the Art reached its truly practical form in America. In the latter part of his statement the professor is correct, but as to the first appearance of the key-driven machine the U. S. Patent Office records show that a patent was issued to D. D. Parmelee in 1850 for a key-driven adding machine (see illustration).

First attempt to use depressable keys for adding was made in America

By referring to the illustration of theParmelee machinereproduced from the drawings of the patent, the reader will notice that the patentee deviated from the established principle of using numeral wheels. In place of numeral wheels a long ratchet-toothed bar has been supplied, the flat faces of which are numbered progressively from the top to the bottom.

Description of Parmelee machine

As shown inFig. 2of these drawings, a spring-pressed ratchet pawl marked k, engages the teeth of the ratchet or numeral bar. The pawl k, is pivoted to a lever-constructed device marked E, the plan of which isshown inFig. 3. This lever device is pivoted and operated by the keys which are provided with arms d, so arranged that when any one of the keys is depressed the arm contacts with and operates the lever device and its pawl k to ratchet the numeral bar upwards.

Another spring-pressed ratchet pawl marked m (see Fig. 2) is mounted on the bottom of the casing and serves to hold the numeral bar from returning after a key-depression.

It will be noted fromFig. 1that the keys extend through the top of the casing in progressively varying heights. This variation is such as to allow the No. 1 key to ratchet up one tooth of the numeral bar, the No. 2 key two teeth, etc., progressively. By this method a limited column of digits could be added up by depressing the keys corresponding to the digits and the answer could be read from the lowest tooth of the numeral bar that protruded through the top of the casing.

It is evident that if the Parmelee machine was ever used to add with, the operator would have to use a pussyfoot key-stroke or the numeral bar would over-shoot and give an erroneous answer, as no provision was made to overcome the momentum that could be given the numeral bar in an adding action.

Foreign digit addersSingle digit adders lack capacity

The foreign machines of the key-driven type were made by V. Schilt, 1851; F. Arzberger, 1866; Stetner, 1882; Bagge, 1882; d’Azevedo, 1884; Petetin, 1885; Maq Meyer, 1886. These foreign machines, like that of Parmelee, according to M. le Colonel d’Ocagne, were limited to the capacity of adding a single column of digits at a time. That is, either a column of units or tens or hundreds, etc., at a time. Such machines,of course, required the adding first of all the units, and a note made of the total; then the machine must be cleared and the tens figure of the total, and hundreds, if there be one, must then be added or carried over to the tens column the same as adding single columns mentally.

On account of these machines having only a capacity for adding one order or column of digits, the unit value 9 was the greatest item that could be added at a time. Thus, if the overflow in adding the units column or any other column amounted to more than one place, it required a multiple of key-depressions to put it on the register. For example, suppose the sum of adding the units columns should be 982, it would require the depression of the 9-key ten times and then the 8-key to be struck, to put the 98 on the machine. This order of manipulation had to be repeated for each denominational column of figures.

Another method that could be used in the manipulation of these single-order or digit-adding machines was to set down the sum of each order as added with its units figure arranged relative to the order it represents the sum of, and then mentally add such sums (see example below) the same as you would set down the sums in multiplication and add them together.

Example of method that may be used with single column adder.

Such machines, of course, never became popular because of their limited capacity, which required many extra movements and caused mental strain without offering an increase in speed of calculation as compared with expert mental calculation. There were a number of patents issued in the United States on machines of this class which may well be named single digit adders.

Some early U.S. patents on single-digit adding machines

The machines of this type which were patented in the United States, preceding the first practical multiple order modern machine, were patented by D. D. Parmelee, 1850; W. Robjohn, 1872; D. Carroll, 1876; Borland & Hoffman, 1878; M. Bouchet, 1883; A. Stetner, 1883; Spalding, 1884; L. M. Swem, 1885 and 1886; P. T. Lindholm, 1886; and B. F. Smith, 1887. All of these machines varied in construction but not in principle. Some were really operative and others inoperative, but all lacked what may be termed useful capacity.

To those not familiar with the technical features of the key-driven calculating machine Art, it would seem that if a machine could be made to add one column of digits, it would require no great invention or ingenuity to arrange such mechanisms in a plurality of orders. But the impossibility of effecting such a combination without exercising a high degree of invention will become evident as the reader becomes familiar with the requirements, which are best illustrated through the errors made by those who tried to produce such a machine.

As stated, the first authentic knowledge we have of an actual machinefor adding is extant in models made by Pascal in 1642, which were all multiple-order machines, and the same in general as that shown in theillustration, page 10.

Calculating machines in use abroad for centuries

History shows that Europe and other foreign countries have been using calculating machines for centuries. Like that of Pascal’s, they were all multiple-order machines, and, although not key-driven, they were capable of adding a number of columns or items of six to eight places at once without the extra manipulation described as necessary with single-order digit adding machines. A number of such machines were made in the United States prior to the first practical multiple-order key-driven calculator.

First key-driven machines no improvement to the Art

This fact and the fact that the only operative key-driven machines made prior to 1887 were single-digit adders are significant proof that the backward step from such multiple-order machines to a single-order key-driven machine was from the lack of some unknown mechanical functions that would make a multiple-order key-driven calculator possible. There was a reason, and a good one, that kept the inventors of these single-order key-driven machines from turning their invention into a multiple-order key-driven machine.

It is folly to think that all these inventors never had the thought or wish to produce such a machine. It is more reasonable to believe there was not one of them who did not have the wish and who did not give deep thought to the subject. There is every reason to believe that some of them tried it, but there is no doubt that if they did it was a failure, or there would be evidence of it in some form.

The U. S. Patent Office records show that one ambitious inventor, Thomas Hill, in 1857 secured a patent on a multiple-order key-driven calculating machine (see illustration), which he claimed as a new and useful invention. The Hill patent, however, was the only one of that class issued, until the first really operative modern machine was made thirty years later, and affords a fine example by which the features that were lacking in the make-up of a really operative machine of this type may be brought out.

Description of the Hill machine

Theillustrations of the Hill machineon the opposite page, reproduced from the drawings of the patent, show two numeral wheels, each having seven sets each of large and small figures running from 1 to 9 and the cipher marked on their periphery. The large sets of figures are arranged for addition or positive calculation, and the small figures are arranged the reverse for subtraction or negative calculation. The wheels are provided with means for the carry of the tens, very similar to that found in the Pascal machine. Each of the two wheels shown are provided with ratchet teeth which correspond in number with the number of figures on the wheel.

Spring-pressed, hook-shaped ratchet pawls marked b, are arranged to be in constant engagement with the numeral wheels. These pawls are each pivotally mounted in the end of the levers marked E, which are pivoted at the front end of the casing.

Hill Patent Drawings

The levers E, are held in normal or upward position by springs f, at the front of the machine. Above each of these levers E, are a series of keys which protrude through the casing with their lower ends resting on the levers. There are but six keys shown in the drawing, but the specification claims that a complete set of nine keys may be supplied for each lever.

The arrangement and spacing of the keys are such that the greater the value of the key the nearer it is to the fulcrum or pivot of the lever E. The length of the key stem under the head or button of each key is gauged to allow depression of the key, the lever E and pawl b, far enough to cause the numeral wheel to rotate as many numeral places as the value marking on the key.

A back-stop pawl for the numeral wheels, marked p, is mounted on a cross-rod at the top of the machine. But one of these pawls are shown, the shaft and the pawl for the higher wheel being broken away to show the device for transferring the tens to the higher wheel.

The transfer device for the carry of the tens is a lever arrangement constructed from a tube F, mounted on the cross-rod m, with arms G and H. Pivoted to the arm G, is a ratchet pawl i, and attached to the pawl is a spring that serves to hold the pawl in engagement with the ratchet of the higher-order numeral wheel, and at the same time, through its attachment with the pawl, holds the lever arms G and H retracted as shown in the drawing.

As the lower-order numeral wheel passes any one of its points from 9 to O, one of the teeth or cam lugs n, on the wheel will move the arm H, of the transfer lever forward, causing the pawl i, to move the higher-order wheel one step to register the accumulation of the tens.

The functions of the Hill mechanism would, perhaps, be practical if it were not for the physical law that “bodies set in motion tend to remain in motion.”

Hill machine at National Museum

Considerable unearned publicity has been given the Hill invention on account of the patent office model having been placed on exhibit in the National Museum at Washington. Judging from the outward appearance of this model, the arrangement of the keys in columns would seem to impart the impression that here was the foundation of the modern key-driven machine. The columnar principle used in the arrangement of the keys, however, is the only similarity.

Inoperativeness of Hill machine

The Hill invention, moreover, was lacking in the essential feature necessary to the make-up of such a machine, a lack that for thirty years held the ancient Art against the inroads of the modern Art that finally displaced it. The feature lacking was a means for controlling the action of the mechanism under the tremendously increased speed produced by the use of depressable keys as an actuating means.

Hill made no provision for overcoming the lightning-speed momentum that could be given the numeral wheels in his machine through manipulation of the keys, either from direct key-action or indirectly through the carry of the tens. Imagine the sudden whirl his numeral wheel would receive on a quick depression of a key and then consider that he provided no means for stopping these wheels; it is obvious that a correct result could not be obtained by the use of such mechanism. Some idea of what would take place in the Hill machine under manipulation byan operator may be conceived from the speed attained in the operation of the keys of the up-to-date modern key-driven machine.

High speed of key drive

Operators on key-driven machines oftentimes attain a speed of 550 key strokes a minute in multiplication. Let us presume that any one of these strokes may be a depression of a nine key. The depression and return, of course, represents a full stroke, but only half of the stroke would represent the time in which the wheel acts. Thus the numeral wheel would be turned nine of its ten points of rotation in an eleven hundredth (¹/₁₁₀₀) of a minute. That means only one-ninth of the time given to half of the key-stroke, or a ninety-nine hundredth (¹/₉₉₀₀) of a minute; a one hundred and sixty-fifth (¹/₁₆₅) part of a second for a carry to be effected.

Camera slow compared with carry of the tens

If you have ever watched a camera-shutter work on a twenty-fifth of a second exposure, which is the average time for a snap-shot with an ordinary camera, it will be interesting to know that these controlling devices of a key-driven machine must act in one-fifth the time in which the shutter allows the daylight to pass through the lens of the camera.

Think of it; a machine built with the idea of offering the possibility of such key manipulation and supplying nothing to overcome the tremendous momentum set up in the numeral wheels and their driving mechanism, unless perchance Hill thought the operator of his machine could, mentally, control the wheels against over-rotation.

Chapin Patent Drawings

Lack of a proper descriptive term used to refer to an object, machine, etc., oftentimes leads to the use of an erroneous term. To call the Hill invention an adding machine is erroneous since it would not add correctly. It is as great an error as it would be to refer to the Langley aeroplane as a flying machine.

Hill machine merely adding mechanism, incomplete as operative machine

When the Wright brothers added the element that was lacking in the Langley plane, a real flying machine was produced. But without that element the Langley plane was not a flying machine. Likewise, without means for controlling the numeral wheels, the Hill invention was not an adding machine. The only term that may be correctly applied to the Hill invention is “adding mechanism,” which is broad enough to cover its incompleteness. And yet many thousands of people who have seen the Hill invention at the National Museum have probably carried away the idea that the Hill invention was a perfectly good key-driven adding machine.

Chapin and Stark patents

Lest we leave unmentioned two machines that might be misconstrued to hold some of the features of the Art, attention is called to patents issued to G. W. Chapin in 1870 (see illustration on opposite page), and A. Stark in 1884 (see illustration on page 32).

Description of Chapin machine

Referring to the illustration reproducing the drawings of the Chapin patent, the reader will note that inFig. 1there are four wheels marked V. These wheels, although showing no numerals, are, according to the specification, the numeral wheels of the machine.

The wheels are provided with a one-step ratchet device for transferring the tens, consisting of the spring frame and pawl shown inFig. 3, which is operated by a pin in the lower wheel.

InFig. 1the units and tens wheel are shown meshed with their driving gears. These gears are not numbered but are said to be fast to the shafts N and M, respectively (see Fig. 2).

Fast on the shaft M, is a series of nine ratchet-toothed gears marked O, and a like series of gears P, are fast to the shaft N. Co-acting with each of these ratchet-toothed gears is a ratchet-toothed rack F, pivoted at its lower end to a key-lever H, and pressed forward into engagement with its ratchet gear by a spring G.

The key-levers H, of which there are two sets, one set with the finger-pieces K and the other with the finger-pieces J, are all pivoted on the block I, and held depressed at the rear by an elastic band L. The two sets of racks F, are each provided with a number of teeth arranged progressively from one to nine, the rack connected with the No. 1 key having one ratchet tooth, the No. 2 having two teeth, etc.

Inoperativeness of Chapin machine

By this arrangement Chapin expected to add the units and tens of a column of numerical items, and then by shifting the numeral wheels and their transfer devices, which are mounted on a frame, designed for that purpose, he expected to add up the hundred and thousands of the same column of items.

It is hardly conceivable that the inventor should have overlooked the necessity of gauging the throw of the racks F, but such is the fact, as no provision is made in the drawings, neither was mention made of such means in the specification. Even a single tooth on his rack F, could, under a quick key-stroke, overthrow the numeral wheels, and the same is true of the carry transfer mechanism.

From the Stark Patent Drawings

The Chapin machine, like that of Hill, was made without thought as to what would happen when a key was depressed with a quick stroke, as there was no provision for control of the numeral wheels against overthrow. As stated, the machine was designed to add two columns of digits at a time, and with an attempt to provide means to shift the accumulator mechanism, or the numeral wheels and carry-transfer devices, so that columns of items having four places could be added by such a shift. Such a machine, of course, offered less than could be found in the Hill machine, and that was nothing at all so far as a possible operative machine is concerned.

Thereproduction of the patent drawingsof the Stark machine illustrated on the opposite page show a series of numeral wheels, each provided with three sets of figures running from 1 to 9 and 0.

Description of Stark machine

Pivotally mounted upon the axis of the numeral wheels at each end are sector gears E¹ and arms E⁴, in which are pivoted a square shaft E, extended from one arm to the other across the face of the numeral wheels. The shaft E, is claimed to be held in its normal position by a spring so that a pawl, E², shiftably mounted on the shaft, designed to ratchet or actuate the numeral wheels forward, may engage with any one of the numeral wheel ratchets.

A bail marked D, is pivoted to standards A¹, of the frame of the machine, and is provided with the two radial racks D³ which mesh with the sector gears E¹. It may be conceived that the act of depressing thebail D, will cause the actuating pawl E², to operate whichever numeral wheel it engages the ratchet of.

The bail D, is held in its normal position by a spring D², and is provided with nine keys or finger-pieces d, eight of which co-act with the stepped plate G, to regulate the additive degree of rotation given to the numeral wheels, while the ninth has a fixed relation with the bail and the bail itself is stopped.

The keys d, marked from 1 to 8, are pivoted to the bail in such a manner that their normal relation to the bail will allow them to pass by the steps on the stepped plate G, when the bail is depressed by the fixed No. 9 key. When, however, any one of the keys numbered from 1 to 8 is depressed, the lower end of the shank of the key will tilt rearward, and, as the bail is depressed, offers a stop against the respective step of the plate G, arranged in its path, thus stopping further action of the actuating pawl E², but offering nothing to prevent the continuation of the force of momentum set up in the numeral wheels by the key action.

There was small use in stopping the action of the pawl E², if the ratchet and numeral wheel, impelled by the pawl, could continue onward under its momentum.

The carry of the tens transfer device is of the same order as that described in the Pascal and Hill machines; that is, a one-step ratchet-motion actuated by a cam lug or pin from the lower wheel. The carry transfer device consists of the lever F, and pawl f⁴, acting on the ratchet of the upper wheel which is operated by the cam lugs b⁵ of the lower wheel acting on the arms f¹ and f³ of the lever F.

From the Robjohn Patent Drawings

Inoperativeness of Stark machine

The machine shown in the Stark patent was provided with but one set of keys, but the arrangement for shifting the driving ratchet pawl E², from one order to another, so that the action of the keys may rotate any one of the numeral wheels, gave the machine greater capacity than the single digit adders; but as with the Chapin machine, of what use was the increase in capacity if the machine would not add correctly. That is about all that may be said of the Stark machine, for since there was no means provided by which the rotation of numeral wheels could be controlled, it was merely a device for rotating numeral wheels and was therefore lacking in the features that would give it a right to the title of an adding machine.

Nine keys common to a plurality of orders

The nine-key scheme of the Stark invention, connectable to the different orders, was old, and was first disclosed in the U. S. Patent to O. L. Castle in 1857 (a machine operated by a clock-spring wound by hand), but its use in either of these machines should not be construed as holding anything in common with that found in some of the modern recording adders. The Castle machine has not been illustrated because it does not enter into the evolution of the modern machine.

The ancient Art, or the Art prior to the invention of Parmelee, consisted of mechanism which could be controlled by friction devices, or Geneva gear-lock devices, that were suitable to the slow-acting type of manipulative means.

The first attempt at a positive control for a key-driven adding device is found in a patent issued to W. Robjohn in 1872 (see illustration).As will be noted, this machine was referred to in the foregoing discussion as merely a single-digit adding machine, having the capacity for adding but one column of digits at a time.

Referring to theillustration of the patent drawingsof the Robjohn machine, it will be noted that there are three sight openings in the casing through which the registration of the numeral wheels may be read. The numeral wheels, like those of all machines of this character, are connected by devices of a similar nature to those in the Hill machine for carrying the tens, one operating between the units and tens wheel and another between the tens and hundredths wheel.

Description of Robjohn machine

The units wheel shown inFig. 3is connected by gearing to a long pin-wheel rotor, marked E, so that any rotation of the rotor E, will give a like rotation to the units numeral wheel to which it is entrained by gearing.

To each of the nine digital keys, marked B, is attached an engaging and disengaging sector gear device, which, as shown inFig. 3, although normally not in engagement with the rotor E, will upon depression of its attached key, engage the rotor and turn it.

A stop device is supplied for the key action, which in turn was supposed to stop the gear action; that seems rather doubtful. However, an alternative device is shown inFigs. 4 and 5, which provides what may without question be called a stop device to prevent over-rotation of the units wheel under direct key action.

From Drawings of Bouchet Patent 314,561

It will be noted that the engaging and disengaging gear device is here shown in the form of a gear-toothed rack and that the key stem is provided with a projecting arm ending in a downwardly projecting tooth or detent which may engage the rotor E, and stop it at the end of the downward key action. While the stopping of the rotor shows a control in the Robjohn machine which takes place under direct action from the keys to prevent overthrow of the units numeral wheel, it did not prevent the overflow of the higher or tens wheels, if a carry should take place. There was no provision for a control of the numeral wheels under the action received from the carry of the tens by the transfer mechanism.

First control for a carried numeral wheel

The first attempt to control the carried wheel in a key-driven machine is found in a patent issued to Bouchet in 1882 (see illustration on opposite page); but it was a Geneva motion gearing which, as is generally known, may act to transmit power and then act to lock the wheel to which the power has been transmitted until it is again to be turned through the same source. Such a geared up and locked relation between the numeral wheels, of course, made the turning of the higher wheel (which had been so locked) by another set of key-mechanism an impossibility.

Theillustration of the Bouchet machineon the opposite page was reproduced from the drawings of the patent which is the nearest to the machine that was placed on the market. The numeral wheels, like most of the single-digit adders, are three in number, and consist of the primeactuated, or units wheel, and two overflow wheels to receive the carry of the tens. The units wheel has fixed to it a long 10-tooth pinion or rotor I, with which nine internal segmental gear racks L, are arranged to engage and turn the units wheel through their nine varying additive degrees of rotation.

Description of Bouchet machine

The segmental gear racks L, are normally out of mesh with the pinion I, and are fast to the key levers E, in such a manner that the first depression of a key causes its rack to rock forward and engage with the pinion I, and further depression moves the rack upward and rotates the pinion and units numeral wheel. It will be noted that this engaging and disengaging gear action is in principle like that of Robjohn.

The transfer devices for the carry of the tens, as already stated, belong to that class of mechanism commonly known as the “Geneva motion.” It consists of a mutilated or one-tooth gear fast to the units wheel operating with a nine-tooth gear, marked D¹, loosely mounted on an axis parallel to the numeral wheel axis. Each revolution of the units wheel moves the nine-tooth gear three spaces, and in turn moves the next higher numeral wheel to which it is geared far enough to register one point or the carry. A circular notched disc, marked S, is fast to the units wheel, and the nine-tooth gear D¹, has part of two out of every three of its teeth mutilated or cut away to make a convex surface for the notched disc to rotate in.

With such construction the nine-tooth gear may not rotate or become displaced as long as the periphery of the disc continues to occupy any one of the three convex spaces of the nine-tooth gear. When, however, the notch of the disc is presented to the mutilated portion of thenine-tooth gear, the said gear is unlocked. This unlocking is coincident to the engagement of the single tooth of the numeral wheel-gear with the nine-tooth gear and the passing of the numeral wheel from 9 to 0, during which the nine-tooth gear will be moved three spaces, and will be again locked as the notch in the disc passes and the periphery fills the next convex space of the mutilated nine-tooth gear.

Bouchet machine marketed

The Bouchet machine was manufactured and sold to some extent, but never became popular, as it lacked capacity. Machines of such limited capacity could not compete with ordinary accountants, much less with those who could mentally add from two to four columns at a clip. Aside from the capacity feature, there was another reason why these single-order machines were useless, except to those who could not add mentally. Multiple forms of calculation, that is, multiplication and division, call for a machine having a multiplicity of orders. The capacity of a single order would be but 9 × 9, which requires no machine at all—a seven-year-old child knows that. To multiply 58964 × 6824, however, is a different thing, and requires a multiple-order calculator.

Misuse of the term “Calculating Machine”

It is perhaps well at this time to point out the misuse of the term calculating where it is applied to machines having only a capacity for certain forms of calculating as compared with machines which perform in a practical way all forms of calculation, that is, addition, multiplication, subtraction and division. To apply the term “calculating machine” to a machine having anything less than a capacity for all these forms is erroneous.

An adding machine may perform one of the forms of calculation, but tocall it a calculating machine when it has no capacity for division, subtraction or multiplication, is an error; and yet we find the U. S. Patent Office records stuffed full of patents granted on machines thus erroneously named. The term calculating is the broad term covering all forms of calculation, and machines performing less should be designated according to their specific capacities.

It is true that adding is calculating, and under these circumstances, why then may not an adding machine be called a calculator? The answer is that it may be calculating to add; it may be calculating to either subtract, multiply or divide; but if a machine adds and is lacking in the means of performing the other forms of calculation, it is only part of a calculating machine and lacks the features that will give it title to being a full-fledged calculator.[1]

Considerable contention was raised by parties in a late patent suit as to what constituted the make-up of a calculating machine. One of the attorneys contended that construction was the only thing that would distinguish a calculating machine. But as machines are named by their functioning, the contention does not hold water. That is to say: A machine may be a calculating machine and yet its construction be such that it performs its functions of negative and positive calculation without reversal of its action.

Again, a machine may be a calculating machine and operate in one direction for positive calculation and the reverse for negative calculation. As long as the machine has been so arranged that all forms of calculation may be performed by it without mental computation, and the machine has a reasonable capacity of at least eight orders, it should be entitled to be called a calculating machine.

Drawings of Spalding Patent No. 293,809

The next machine that has any bearing on the key-driven Art of which there is a record, is illustrated in a patent granted to C. G. Spalding in 1884 (see illustration on opposite page). The Spalding invention, like that of Bouchet, was provided with control for its primary actuation and control for its secondary or carrying actuation.

Description of Spalding machine

Referring to theSpalding machinereproduced from the drawings of his patent, the reader will note that in place of the units and tens numeral wheels, a clock hand has been supplied, co-operating with a dial graduated from 0 to 99, showing the figures 5, 10, 15, etc., to 95, for every five graduations.

Another similar hand or arrow and dial to register the hundreds is also provided, having a capacity to register nineteen hundred. Attached to the arrows, through a shaft connection at the back of the casing are ratchet wheels, having respectively the same number of teeth as the graduation of the dial to which each hand belongs.

Co-operating with the hundred-tooth ratchet of the units and tens register hand is a ratchet and lever motion device (see Fig. 2) to turn the arrow from one to nine points of the graduation of the dial. The ratchet and lever motion device consists of the spring-pressed pawl E, mounted on the lever arm D, engaging the hundred-tooth ratchet, the link or push-rod F, the lever G, and its spring O. It will be noted that a downward action of the lever G, will,through the rod F, cause a like downward action of the lever D, causing the ratchet pawl E to be drawn over the ratchet teeth. Upon the release of the lever G, the spring O, will return it to its normal position and through the named connecting parts, ratchet forward the arrow.

The normal position of the pawl E is jammed into the tooth of the ratchet and against the bracket C, that forms the pivot support for the pivot shaft of the arrow. This jammed or locked combination serves to stop the momentum of the ratchet wheel at the end of the ratcheting action, and holds the wheel and its arrow normally locked until the lever G is again depressed.

The means for gauging the depression and additive degrees of action of the lever G is produced through the slides or keys marked a, having finger-pieces c, springs f, and pins e, bearing against the top of the lever G, combined with what may be called a compensating lever marked K.

The specification of the patent states that the depression of a key will depress the lever G and the free end will engage the bent end t, of the compensating lever K, and rock its envolute curved arm M, upward until it engages the pin e of the key, which will block further motion of the parts.

The effectiveness of the construction shown for the lever K is open to question.

Prime actuation of a carried wheel impossible in the Spalding machine

The carry of the hundreds is accomplished by means of a one-step ratchet device represented by the parts lever R, pawl T, spring P, and operating pin g. When the hundred-tooth ratchet nears the end of its revolution, the pin g, made fast therein, engages the free end of the ratchet lever R, and depresses it; and as the hand attached to thehundred-tooth ratchet wheel passes from 99 to 0 the pin g passes off the end of the ratchet lever R, and the spring P retracts the lever ratcheting the twenty-tooth wheel and its arrow forward one point so that the arrow registers one point greater on the hundreds dial.

Although the Spalding means of control under carrying differed from that of Bouchet in construction, its function was virtually the same in that it locked the carried or higher wheel in such a manner as to prevent the wheel from being operated by an ordinal set of key mechanism.

And the control under key action would prevent a carry being delivered to that order through the locked relation of the ratchet and pawl E.

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