<P> MacKellar's The American Printer was the dominant language style guide in the US at the time and ran to at least 17 editions between 1866 and 1893, and De Vinne's The Practice of Typography was the undisputed global authority on English - language typesetting style from 1901 until well past Dowding's first formal alternative spacing suggestion in the mid-1950s . Both the American and the UK style guides also specified that spaces should be inserted between punctuation and text . The MacKellar guide described these as hairspaces but itself used a much wider space than was then commonly regarded as a hairspace . Spaces following words or punctuation were subject to line breaks, and spaces between words and closely associated punctuation were non-breaking . Additionally, spaces were (and still are today) varied proportionally in width when justifying lines, originally by hand, later by machine, now usually by software . </P> <P> The spacing differences between traditional typesetting and modern conventional printing standards are easily observed by comparing two different versions of the same book, from the Mabinogion: </P> <Ol> <Li> 1894: the Badger - in - the - bag game--traditional typesetting spacing rules: a single enlarged em - space between sentences </Li> <Li> 1999: the Badger - in - the - bag game--modern mass - production commercial printing: a single word space between sentences </Li> </Ol> <Li> 1894: the Badger - in - the - bag game--traditional typesetting spacing rules: a single enlarged em - space between sentences </Li>

When did we stop putting two spaces after a period