There is (debated) speculation that Gutenberg made several forms of some letters with different widths so that he could justify lines with very small adjustment

There is (debated) speculation that Gutenberg made several forms of some letters with different widths so that he could justify lines with very small adjustments rather than adding space between words. The Wikipedia microtypography page has more details: http://en.wikipedia.org/wiki/Microtypography http://en.wikipedia.org/wiki/Microtypography