Webmaster Forum / HTML, CSS, Scripts / CSS / May 2008

http://en.wikipedia.org/wiki/French_spacing includes 10 citations
(numbers 6 to 15) that might be what you are looking for.

The practise seems to be falling out of favour, so there are no doubt
style guides that recommend the same width of space in all cases, but
unless the citations in that article are wrong, there have been guides
and authorities that support this widely held view.

[...]

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A neater way of doing it might be to surround each sentence with <span
class="sentence">...</span>.

Then use

.sentence { padding-right: 0.25em }
.sentence:after { content: "." }

Or not bother with the :after (which is unsupported in IE probably, and
a bit silly here anyway) and just type the .s in.

Jeremy schrieb:

Note that not every "." followed by whitespace marks the end of a
sentence (e.g. <- abbreviations).

In the typewriter era, the standard business practice was ALWAYS two spaces
after a period. Only with the introduction of computers with proportional
space fonts did this standard give way, and it didn't go down without a
fight from the traditionalists.

I wrote up a message about this and then just left it since I did not
think there were any real matters of fact in dispute -- while there
were some rather dismissive remarks, no one actually said that there
had never been any authority to support this view.

Note that I used the past tense.  I don't think any current authority
supports the practise, but there is no doubt that it was once the
norm.  For example, the 1911 edition of the Chicago "Manual of
Style"[1] has this to say:

 A standard line should have a 3-em space between all words not
 separated by other punctuation points than commas, and after commas;
 an en-quad after semicolons, and colons followed by a lower-case
 letter; two 3-em spaces after colons followed by a capital; an
 em-quad after periods, and exclamation and interrogation points,
 concluding a sentence.

(a 3-em space is a three-to-an-em space, or 1/3em).

At some point between then and now this changed to the current advice
which states that a regular word space is to be used after the
punctuation that ends a sentence (reference: current (2008) on-line
version of Manual of Style -- subscription only).

That there was a change already afoot, resisted by traditionalists, is
evidenced by the only reference to inter-sentence space in the
otherwise comprehensive "Correct Composition"[2] by Theodoee Low de
Vinne.  On page 203 there is a footnote:

 Thin spacing is practised by several eminent disciples of the
 fifteenth-century school of typography, apparently on these
 grounds: As the early printers made exclusive use of one thin space,
 we should use the thin space only. It is held that this thin space
 is wide enough to separate words and even sentences

 The em quadrat between sentences and the three-to-em space between
 words are rated as waste white space, and are a vexation to one who
 admires the mannerisms of medieval copyists.

The standard rule is only referred to obliquely, it seems to be so
wide-spread.  The tone is not flattering to these radicals.  In
another book by de Vinne (which I can't find right now) the rule is
again referred too only obliquely by stating that when spaces between
words have to be reduced from the normal 1/3em, the em quadrat between
sentences can be reduced to an en quadrat.

As early as 1913, in the beautifully printed "Type Spacing" by E R
Currier, we read[2]:

 The best typographers have already discovered that there is no good
 reason for following the practice of inserting a full em-quad
 between sentences.  As punctuation the em-quad is really
 superfluous, since the presence of the period and capital provide
 sufficient emphasis over the spacing between other words in the line
 to mark the new sentence.

Although I am sure that a /little/ extra space is used between
sentences, even in this text.  Judge for yourself at [4].

The practise continued well into the computer era.  It was the norm in
troff and survived into the Plan 9 version (see section 4.1 in [5]).
Of course, TeX does something similar (it uses glue with more stretch
between words) to this day.  These of course are not authorities --
just places where the traditional rule refuses to die.

I will miss it.  I like the look (although the full em-quadrant used
in early 20th century books does look huge these days) and I think it
particularly lacking on the web, where that little extra space helps
with all those ridiculous small fonts people keep suggesting to my
browser!

----------------
[1] "Manual of style, a compilation of the typographical rules in
 force at the University of Chicago press, with specimens of types in
 use at the University press", University of Chicago Press, Chicago,
 Ill, 1911.

[2] Theodoee Low de Vinne, "Correct Composition: A Treatise On
 Spelling Abbreviations, The Compounding And Division Of Words, The
 Proper Use Of Figures And Numerals, Italic And Capital Letters,
 Notes, Etc.  With Observations On Punctuation And Proof-Reading",
 Second Edition, New York, The Century Co., 1904

[3] E. R. Currier, "Type Spacing", J. M. Bowles, New York, 1913.

[4] Image of page 1 of the above:
 http://bsb.me.uk/tmp/type-spacing.jpg

[5] B. W. Kernighan, "Troff User's Manual", Plan 9 Ed. (at
 http://plan9.bell-labs.com/sys/doc/troff.pdf).