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Printing Terminals and Proportional Spacing

The IBM Executive typewriter allowed typed documents to somewhat resemble typeset text by varying the amount of space allocated to different letters. For example, with the Documentary font, a character could be from 2 to 5 units in width, where each unit was 1/32 of an inch. Other fonts, even when still typed at 6 lines to the inch, had a different basic unit; the Mid-Century font, for example, used a unit of 1/36 of an inch.

Using a crude dot-matrix font, the diagram below illustrates a unit system of this type:

and this keyboard chart includes typical character widths for such a unit system:

 -----------------------------------------------
| ! | @ | # | $ | % | ¢ | & | * | ( | ) | _ | + |
|  2|  5|  3|  3|  5|  3|  4|  3|  2|  2|  5|  3|
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 0 | - | = |
|  3|  3|  3|  3|  3|  3|  3|  3|  3|  3|  3|  3|
 -----------------------------------------------
  | Q | W | E | R | T | Y | U | I | O | P | ¼ |
  |  4|  5|  4|  4|  4|  4|  4|  2|  4|  4|  5|
  | q | w | e | r | t | y | u | i | o | p | ½ |
  |  3|  4|  3|  3|  2|  3|  3|  2|  3|  3|  5|
   --------------------------------------------
   | A | S | D | F | G | H | J | K | L | : | " |
   |  4|  3|  4|  4|  4|  4|  3|  4|  4|  2|  3|
   | a | s | d | f | g | h | j | k | l | ; | ' |
   |  3|  3|  3|  2|  3|  3|  2|  3|  2|  2|  2|
    -------------------------------------------
     | Z | X | C | V | B | N | M |   |   | ? |
     |  4|  4|  4|  4|  4|  4|  5|   |   |  3|
     | z | x | c | v | b | n | m | , | . | / |
     |  3|  3|  3|  3|  3|  3|  5|  2|  2|  3|
      ---------------------------------------

space = 2

2 fijlt I .,:;'!()
3 abcdeghknopqrsuvxyz JS 0123456789 "?#+-*/= 
4 w ABCDEFGHKLNOPQRTUVXYZ &
5 m WM @%_½¼

This is based on the unit system for Documentary at a unit size of 1/32", but may deviate from it for some of the special characters, my actual primary source being a font with the same spacing as Documentary for the letters which was used on a Friden Justowriter.

While we are on the topic of IBM trivia, and if we have wandered from punched card codes to line printers, another important input-output device, the IBM 2741 printing terminal, may also deserve some attention.

In the top two rows of this diagram, the two major families of 2741 arrangements are illustrated, first the arrangement of characters on the keyboard, and then the arrangement of characters on the typing element.

The arrangement at the top, the Correspondence arrangement, uses exactly the same elements as a standard office Selectric typewriter. The one in the middle is the PTTC/EBCD arrangement, which is designed so that the position of characters on the element leads to a code for the letters which has some relation to punched card codes and the EBCDIC internal code.

On the bottom is the keyboard arrangement, and arrangement of characters on the element, for another major family of devices using the IBM Selectric "golfball" element, but which was not made into a form of the 2741 terminal.

The charts of 2741 codes on the right shows the codes for the printing characters applicable to the Correspondence arrangement and then for the PTTC/EBCD arrangement; the relation between these is determined by matching characters in corresponding positions on the elements. The space and control characters always have the same codes.

Now that we have discussed the IBM Selectric Composer, here is a chart of its keyboard, including the widths of each of its characters in units, a unit being 1/72", 1/84", or 1/96" depending on the size of type being set, these sizes being indicated by red, yellow, and blue triangles upon the element respectively:

 -----------------------------------------------
| ! | † | + | $ | % | / | & | * | ( | ) | _ | @ |
|  4|  6|  6|  6|  8|  4|  8|  6|  4|  4|  8|  8|
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 0 | - | = |
|  6|  6|  6|  6|  6|  6|  6|  6|  6|  6|  3|  6|
 -----------------------------------------------
  | Q | W | E | R | T | Y | U | I | O | P | ¼ |
  |  8|  9|  7|  8|  7|  8|  8|  4|  8|  6|  8|
  | q | w | e | r | t | y | u | i | o | p | ] |
  |  6|  8|  5|  4|  4|  6|  6|  3|  6|  6|  6|
   --------------------------------------------
   | A | S | D | F | G | H | J | K | L | ¾ | ½ |
   |  8|  6|  8|  7|  8|  8|  5|  8|  7|  8|  8|
   | a | s | d | f | g | h | j | k | l | ? | [ |
   |  5|  4|  6|  4|  5|  6|  3|  6|  3|  5|  5|
    -------------------------------------------
     | Z | X | C | V | B | N | M | ` | ' | : |
     |  7|  8|  7|  8|  7|  8|  9|  3|  3|  4|
     | z | x | c | v | b | n | m | , | . | ; |
     |  5|  6|  5|  6|  6|  6|  9|  3|  3|  3|
      ---------------------------------------

space = 3

3 ijl  .,;`'-
4 ftrs  I  :!()/
5 acegz  J  [
6 bdhknpquvxy  PS  0123456789  ]+*=$†
7 BCEFLTZ
8 w  ADGHKNOQRUVXY &@%½¼¾ <em dash>
9 m  WM

where the underscore is filling the space that should contain a dash (I've seen pages that try to use &emdash; but that doesn't work), and I have cheated somewhat by using † or &#134; to represent a dagger, which assumes you are viewing the page from within Microsoft Windows. The difference in width between colon and semicolon, and open and close square bracket, is intentional, and has to do with the desired amount of space after each character.

And, while we're on this topic, here is my attempt at a reconstruction of the unit system of the Mag Card Executive:

 -----------------------------------------------
| ! | @ | # | $ | % | ¢ | & | * | ( | ) | _ | + |
|  5|  5|  5|  5|  5|  5|  5|  5|  5|  5|  5|  5|
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 0 | - | = |
|  5|  5|  5|  5|  5|  5|  5|  5|  5|  5|  5|  5|
 -----------------------------------------------
  | Q | W | E | R | T | Y | U | I | O | P | ¼ |
  |  7|  7|  6|  7|  7|  7|  7|  4|  7|  6|  5|
  | q | w | e | r | t | y | u | i | o | p | ½ |
  |  6|  7|  5|  5|  4|  6|  5|  3|  5|  6|  5|
   --------------------------------------------
   | A | S | D | F | G | H | J | K | L | : | " |
   |  7|  6|  7|  6|  7|  7|  5|  7|  6|  5|  5|
   | a | s | d | f | g | h | j | k | l | ; | ' |
   |  5|  5|  6|  4|  6|  5|  3|  5|  3|  5|  4|
    -------------------------------------------
     | Z | X | C | V | B | N | M |   |   | ? |
     |  6|  7|  7|  7|  7|  7|  7|   |   |  5|
     | z | x | c | v | b | n | m | , | . | / |
     |  5|  5|  5|  5|  6|  5|  7|  5|  5|  5|
      ---------------------------------------

space = 5

3 ijl
4 ft  I  '
5 acehknorsuvxz J 0123456789 .,:;!?"@#$&¢()+-*/=_½¼
6 bdgpqy EFLPSZ
7 mw ABCDGHKMNOQRTUVWXY 

Although the Mag Card Executive is a rare machine, the same typefaces were used with the 96-character elements for the Model 50 Electronic Typewriter from IBM. This typewriter also typed in pica (1/10" monospaced) and elite (1/12" monospaced), and so I am confident that the unit size for this typewriter, and the Mag Card Executive, was 1/60", although at least one paper published in the IBM Journal of Research and Development claims a 1/72" unit for the Mag Card Executive. Comparing the spacing of this font to that of others, it can be seen that the spacing was designed for a font with a large x-height, the widths of the lower-case letters being larger in relation to those of the upper-case letters than in the other examples. Characters like @, %, and & were specifically designed to fit into the same relatively narrow space as digits to make it easier for typists to still put tables of numbers in uniform columns, even when some special symbols are used.

There may well be serious inaccuracies in the chart above, and someone out there with a Model 50 Electronic Typewriter, or a Model 65 or Model 85 may well be able to supply corrections. The forwards-pointing triangle on a Selectric Composer element indicated its spacing with its color; on a typewriter, a solid white triangle indicated pica, and a hollow triangle elite; proportional spacing was indicated by a circle, both on Model 50 elements and on those for the Mag Card Executive.

The 1/60" unit for proportional spacing of typed copy was, of course, also used on virtually all daisywheel printers that provided proportional spacing. A few even provided the option of printing small monospaced typing with letters 1/15" in width. Rather than being similar to the Mag Card Executive font, however, the proportionally-spaced fonts for some daisywheel printers tended to have small x-heights, a clear distinction between small and capital letters emphasizing that the font in use is proportionally-spaced.

Devoting all this space to unit systems and character widths, I might as well go "whole hog", and present this little cross-reference of some historical font metrics:

Characters Font, Device
12-point Oldstyle type, Foundry (1/4 point) Times Roman, Monotype Graphotype (improved) IBM Selectric Composer (1/72" for 11 point) IBM Mag Card Executive (1/60") Diablo 630 (1/60") Self-Spacing Type Quick-Set Roman Typotabular Gothic No. 4 (1/72") Graphotype (original) Documentary, IBM Executive; Friden Justowriter (1/32") Mid-Century, IBM Executive (1/45") Varityper No. 17 with Condensed Title No. 5, Linotype (1/36") Raphael, Underwood
i j l 15 5 5 3 3 (add I)
3
2 A (I: 3 units)
2
2 2 2 2 1 1
f 6 6 4 4 (remove I)
4
t 17 1/2 3 3
I 7 7 (add Z)
2
2
r (remove g, y)
5
(add o)
B
3
s (J: 3 units)
4
3
c e z 21 8 (g, v, x, y: 9 units)
8
5 5 3
J 4
a g v (add o)
(remove g, x)
(0, 1, 2, 3, 4, 5, 6, 7, 8, 9: 24 units)
25
9 (add Z)
4
(remove o)
C
x y 0 1 2 3 4 5 6 7 8 9 6
h k n o u (add g, x)
27
10 (b, d, o, p, q: 9 units)
10
b d p q (add g, y)
6
S (add Z)
11
6 3
P 33 11 6 (remove w, X, Z)
5
5 4 4 (remove Z)
3
B E F L Z 12 (remove E, T, Z)
12
7
T (remove w)
(add A,U)
35
7
C 13 7 D 4
w V (remove w, G, R, X)
(add D,E,T)
13
8
A G O Q R X Y (add w, K)
(remove A, U)
38
14
D N U 15 (add w, G, R, X)
(remove D, H)
14
H K (remove K)
40
(add w, X)
6
6
m 9 8 5
M 18 (add H)
15
7 5
W 50 16

For the oldstyle foundry type shown in the first column of the table, the digits are oldstyle or non-ranging digits, and this may be a reason that they are somewhat narrower.

Note that the lowercase letter g is narrower than the digits on the Selectric Composer, and the lowercase letters g and y are both narrower than the lowercase letters h, k, n, o, and u in Monotype Times Roman, while on the Mag Card Executive, lowercase g and y are wider than the digits and the lowercase letters h, k, n, o, and u, and, thus, there is a note to that effect in its column, as these letters cannot merely be displaced to an adjacent row in the diagram.

Similarly, other letters are moved around in Self-Spacing Type, a special kind of foundry type originally created by Linn Boyd Benton, the father of Morris Fuller Benton, which was designed to a unit system as an aid to the setting of tabular matter.

In addition to having a unit system, it had one other thing in common with the IBM Selectric Composer. The IBM Selectric Composer used only three sizes of unit, 1/72", 1/84", and 1/96". It allowed margins to be set, and tab stops to be placed, at locations spaced one-sixth of an inch apart. (Note that the unit sizes actually had 1/12" as a common multiple.)

Although it had only three unit sizes, more than three point sizes were offered of several of its more popular typefaces; this led to the problem (as noted, for example, in Production for the Graphic Designer) that changing the point size of text might only change the size of the text in the vertical direction, producing less impact than expected for copyfitting purposes. This also meant that some sizes of a typeface would be slightly more or less condensed than others.

The units for Self-Spacing Type were also subdivisions of the Pica em. While Selectric Composer units were 12, 14, and 16 to the Pica em, Self-Spacing Type units were 7, 8, 9, 10, 11, and 12 to the Pica em.

Later, another form of type based on this principle, Quick-Set Roman, was made and sold by American Type Founders. Instead of using units which were different fractions of the Pica em, the fundamental unit was 1/2 point, or 1/144", although the effort was made to minimize the use of half points. Characters were made in only four different widths, and which character was assigned to which width did not vary with the size of the type, but the ratios between the various widths were allowed to change. The four widths for 6, 8, 10, and 12-point type, as given in the 1923 ATF catalog, and the widths for 14 and 18-point type, of which specimens are also given, are noted in the table below:

Point Size: 6 8 10 12 14 18
A 2 3 4 5 6
B 4 5 6 7 9
C 4 5 6 7 9 12
D 8 9 12 16

Despite the greater limitation in the variation of the widths of the characters, this later form of type seems to me to have been more attractive in appearance than Self-Spacing Type, its predecessor.

In addition to also making monospaced Mailing List Type, there was yet another unitized font for rapid setting available from ATF; this was their line of Typotabular Gothics. Most of these faces resembled Copperplate Gothic, but there was also a condensed gothic as well. These were all-caps fonts, with I (and sometimes J and 1) being one unit wide, and all other characters two units wide. There was only one exception to this, Typotabular Gothic No. 4, which did have lowercase, and four different sizes of characters; this one is shown in the table above.

A table in the famed reference work Typographical Printing-Surfaces, by L. A. Legros and J. C. Grant, giving the widths of the characters in two fonts of foundry type, one a modern typeface and one an oldstyle typeface, appears to indicate that a unit system was in use for foundry type as well:

Units     Points    Inches    Modern           Oldstyle
 16 2/3    12 1/2   0.17296                    W
 16        12       0.16604   W+=@             +=
 13 1/3    10       0.13837                    HMm@
 12 2/3     9 1/2   0.13145   KMm              DGKNOQRXw&
 12         9       0.12453   HGNUX$
 11 2/3     8 3/4   0.12107                    ACTUVY
 11 1/3     8 1/2   0.11761   ADEOQRVY
 11         8 1/4   0.11416                    BEFLPZ$
 10 2/3     8       0.11070   BCFLTw%&
 10         7 1/2   0.10378   PZ
  9         6 3/4   0.09340                    Sbdghknopqux
  8 2/3     6 1/2   0.08994   SJbdghknpqu
  8 1/3     6 1/4   0.08648                    aovy
  8         6       0.08302   vxy1234567890*   1234567890*%
  7 1/3     5 1/2   0.07610   ao
  7         5 1/4   0.07264   ce               Jcez
  6 1/3     4 3/4   0.06573   Irs?
  5 5/6     4 3/8   0.06054                    Irst-/?
  5 1/3     4       0.05535   fjt
  5         3 3/4   0.05189                    fijl[]()
  4 2/3     3 1/2   0.04843   il-/[]()
  4         3       0.04151   .,:;'!           .,:;'!

The fundamental unit is 1/6 of the unit used, but note that only once is the unit split into sixths, and there does seem to be a preference for whole units as opposed to thirds of units. As 13 1/3 units, or 40/3 units, equals 10 points, 1/3 unit appears to be 1/4 of a point, and 1/6 unit appears to be 1/8 of a point. There is reason to believe that the practice was not to scale the unit size with the size of the type, but rather to have the widths of all type slugs as multiples of 1/4 point or 1/8 point, since several ATF catalogues note that spaces which are nominally 3-to-em, 4-to-em, or 5-to-em in fact have their sizes altered so as to be multiples of 1/4 point, as shown below:

Point size:    6      7      8      9     10     11     12     14
            -----------------------------------------------------
3 to em        2      2 1/2  3      3      3 1/2  3 1/2  4      5
4 to em        1 1/2  1 3/4  2      2 1/4  2 1/2  2 3/4  3      4
5 to em        1 1/4  1 1/2  1 1/2  1 3/4  2      2 1/4  2 1/2  3

Optical Scaling

One characteristic of the IBM Selectric Composer is that it had three possible unit sizes, to permit a range of horizontal scalings; a unit could be 1/72", 1/84", or 1/96". Tab stops and margins could be placed at 1/6" intervals. (Because printers usually think of horizontal distances in ems, while points and picas apply to vertical distances, a horizontal distance of 1/6" is normally called a pica em in printing rather than just a pica.) However, 72, 84, and 96 are all multiples of 12.

Because there were only these three sizes, sometimes changing to a different point size of a typeface did not change its horizontal spacing, and some sizes appeared visibly more condensed than others. Let us imagine that someone were to bring out a daisywheel typewriter based on the ideas behind the Selectric Composer, but removing its limitations. Thus, for example, M and W would be increased in size from 9 units to 11 units.

Let us suppose the available unit sizes on such a typewriter are:

1/54", 1/60", 1/66", 1/72", 1/78", 1/84", 1/90", and 1/96".

It might also have a number of alternate assignments of units to the individual letters, so as to permit the printing of smaller type with a coarser unit system, or larger type with a finer unit system.

Even with eight different unit sizes instead of three, the sizes of the units are aliquot parts of one-sixth of an inch, instead of multiples of a finer unit. So the relation of sizes between them won't correspond exactly to the point sizes of type.

This, however, is not as much of a problem as it might seem. In general, as a typeface is reduced to smaller point sizes, it is also widened (and, as well, made bolder). As an example of this, Times New Roman on the Monotype followed this pattern, in part:

Point     Set       Stretch
-----     ---       -------
11        10 1/2     -4.5%
10         9 3/4     -2.5%
 9         9          0
 8         8 1/4      3.1%
 7         7 3/4     10.7%
 6 1/2     7 1/4     11.5%
 6         6 3/4     12.5%

where "Set" means that the Monotype machine's system of 18 horizontal units to the em is applied as if the point size of the type were the figure given in that column, rather than the vertical size of the type.

Another example of optical scaling would be the different sizes of Century Expanded as provided by American Type Founders:

Point      Width      Stretch
-----      --------   -------
11         13 1/2      0
 8         14 1/2      7.4%
 6         15 1/2     14.8%
 5 1/2     17         25.9%

where "Width" is the width of the lower-case alphabet in ems.

While optical scaling was a part of type design even in the days when type designs were realized through punch-cutting, when this firm used the pantograph to make matrices for new type designs more quickly and with a more polished finish, it also made the degree of optical scaling required explicit as part of the new process.

On a Selectric Composer, an 11-point type might have a unit size of 1/72". If we allocated other sizes of type to unit sizes from the expanded scale of units noted above, the results could be:

Point     Unit       Stretch
-----     ----       -------
15        1/54"      -2.2%
12        1/66"       0
11        1/72"       0
10        1/78"       1.5%
 9        1/84"       4.8%
 8        1/90"      10%
 7 1/2    1/96"      10%

and thus all of these choices, at least, would be quite reasonable.


As noted, one of the limitations of the Selectric Composer is that the capital M and W were not as wide as they should have been, in proportion to the other letters, in order to allow reasonably large sizes of type within the limitations of the size of the Selectric typewriter element, oritinally designed for use for normal monospaced typing.

Flexible Spacing

Another limitation is that all the typefaces had exactly the same spacing for each character. Later electronic versions of the Selectric Composer allowed a two-digit type code to be entered, permitting a different arrangement of spacing to be used with Cyrillic elements and for elements which contained two sizes of fonts like Copperplate Gothic, where a smaller size of capital letters replaced the lower case.

In general, this is not normally a problem for most typefaces in normal use. However, the proportions of the capital letters of some oldstyle typefaces are patterned after classic Roman carved letters, such as those on the famous Trajan column, in which case the capital letters B, E, F, L, and P, among others, are more noticeably narrower than most other capital letters than is the case in more ordinary typefaces.

Also, there are typefaces in which the size of the small letters relative to that of the capital letters is unusually small.

The chart above shows how a unit system derived from that of the Selectric Composer could be augmented with two alternative spacings for these cases. Note that capital J has become narrower in both additional settings; that is because, in the fonts concerned, it descends below the line, and thus is kerned: that is, part of the letter overprints the space alloted to the preceding letter.

It can also be noted that in these diagrams, the typefaces shown are in different point sizes, so that the width of the lower-case alphabet is very nearly the same for each one. Since the relative widths of the lower-case letters do not change as noticeably as the widths of some upper-case letters between typefaces, keeping their size fixed reduces the amount of change needed to match the different typefaces.

Also, in preparing this diagram, I examined three typefaces as examples of an old style typeface in which the classical proportions of the capital letters were used. There was a noticeable difference in the relative sizes of small letters and capital letters between those three faces, and the one in the middle was chosen as the example.

While still restricting the number of alternative spacings, there are a few other possibilities not shown here. The width of the capital J is something of a compromise value; a number of typefaces call for it to be made one unit wider rather than one unit narrower. Also, there are the newspaper legibility faces with a very large x-height; reducing the width of the capital letters 8 or more units in width by one unit may be appropriate for them.

The diagram above illustrates how these additional cases might be handled.

Another thing to consider, which involves relatively subtle changes, is how the widths of the characters may vary somewhat when going to italics and boldface:

Also depicted is the appropriate spacing for small capitals, which, of course, is not a subtle variation, but an entirely new series.

However, there are further variations in some fonts that might be worth accomodating, as illustrated above. Given, though, that the capital letters are not used as frequently as the lower-case letters, which have much less variation in widths from one typeface to another, it is understandable how it was possible to get away with one unit system for all typefaces.

Small Capitals

The appropriate proportions for small capitals are a question worthy of some examination. The Selectric Composer had available features that would allow it to vary the spacing of some letters, so that it could use Copperplate Gothic elements which had the capital letters in a smaller size as the lower case. The spacing involved was:

    Upper           Lower         Small
    Case            Case          Capitals

3                   ijl           I
4   I               frst          J
5   J               acefvz        LPSTZ
6   PS              bdhknopquxy   ABCDEFGHKNOQRUVXY
7   BCEFLTZ                       MW
8   ADGHKNOQRUVXY   w
9   MW              m

Here, the ratio of the two sizes appears to be about 3:4.

But Copperplate Gothic might not be a good example to use. To get a trustworthy example for the proportions of small capitals in a normal text face, and for that matter to address the question of italics and boldface, it makes sense to resort to the Monotype matrix-case; one example being that for Times New Roman, series 327:

   Normal                         Italics                Bold

   Upper   Lower       Small      Upper     Lower        Upper   Lower
   Case    Case        Capitals   Case      Case         Case    Case

 5          ijl        I                    ijl                  ijl
 6          ft         J                    ft                   ft
 7 I        rs         S          I         rs           I       rs
 8 J        cez        EF                   cevz                 cevz
 9          agvxy      BLPT       J         abdghnopuy           abdghnopquy
10 S        bdhknopqu  ACOQRVXYZ            kx           J       kx
11 P                   GDHKNU     FS                     FS
12 BEFLTZ              M          BELPT     w            BELPT   w
13 CV       w                     AGKRVXYZ               ACKRXZ
14 AOQRXY                         DNOQU     m            DGNU    m
15 DGHKUN   m          W          H                      HOQ
18 MW                             MW                     MW

Uniform Proportions

On this page, I note that, prior to the adoption of a uniform point system for printing, one James Fergusson adopted a scheme which approximated the old named type sizes by dividing a unit of fourteen lines of Nonpareil type, or seven picas, into different parts, just as the Selectric Composer divided the pica em into different numbers of parts.

In order to allow small type sizes to be handled, the actual unit that would have to be divided would be one of 42 points, of which the circumference of the roller would have to be a multiple. Since dividing it into 6 parts yields 7 points, and into 7 parts yields 6 points, those two of the six possible sizes would not require additional gears, so only four additional gears would be left:

(7 points)  Minion    (7 points)  x2 English       x4 Two-line English
(6 points)  Nonpareil (6 points)  x2 Pica          x4 Double Pica
 8 parts    Agate     (5.25)      x2 Small Pica    x4 Two-line Pica
 9 parts    Pearl     (4.66667)   x2 Long Primer   x4 Paragon
10 parts    Diamond   (4.2)       x2 Bourgeois     x4 Great Primer
11 parts    Brilliant (3.81818)   x2 Brevier       x4 Columbian

In order to match this up with the horizontal divisions, so that no rescaling of typefaces would be required between sizes, one could use the 1/72" unit for English, the 1/84" unit for Pica, the 1/96" unit for Small Pica. Since 11 point type, rather than 14 point type, was used with the 1/72" unit, this would mean a unit system that was more finely grained for those sizes of types; for smaller sizes, though, the number of units to the em would need to be divided in half, so instead of 11 units to the em, either 14 or 7 units would be used.

The fact that these scales would only coincide every 42 points would create a limitation in their use. One way this difficulty could be reduced is this: if the normal gear for advancing the platen according to the point system operates in steps of 1/144", then it would not be unreasonable for the four additional gears to divide the basic 42 point space not into 8, 9, 10, and 11 parts respectively, but into 56, 63, 70 and 77 parts. One would still need 11 lines of Brevier to add up to exactly 84 points, but now those 11 lines could start at any position that was a multiple of 6 points. As well, the diameter of the roller would now only have to be a multiple of 6 points instead of a multiple of 42 points, so that a standard typewriter roller could be used without a change in its diameter.


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