[Sidenote: _First attempt to use depressable keys for adding was made
in America_]
By referring to the illustration of the Parmelee machine reproduced
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.
[Sidenote: _Description of Parmelee machine_]
As shown in Fig. 2 of 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
is shown in Fig. 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 from Fig. 1 that 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.
[Sidenote: _Foreign digit adders_]
[Sidenote: _Single 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.
982
563
384
125
-------
170012
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.
[Sidenote: _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 machine
for 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 the
illustration, page 10.
[Sidenote: _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.
[Sidenote: _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.