Robert_Charlton - 8:20 am on Dec 18, 2010 (gmt 0)
I'm off to upset my broadband provider...
...and with older fonts, the OCR tends to be poor. As you go even further back and spellings get less consistent, the OCR tends to mangle words more often.
I'm surprised the OCR is as good as it is, particularly on the "long" or "medial s" character that resembles an "f". The Ngram info page [ngrams.googlelabs.com] cites this character as a common cause of misspellings and refers us to this Wikipedia article....
The article suggested to me at least a rough way of quantifying the error...
The long s fell out of use in roman and italic typefaces well before the middle of the 19th century; in France the change occurred from about 1780 onwards, in Britain in the decades around 1800, and some twenty years later in the United States. This may have been spurred by the fact that long s looks somewhat like an f (in both its roman and italic forms), whereas short s did not have this disadvantage, making it easier to identify, especially for people with problems of vision.
I ran comparisons for the following pairs to get an indication of whether common f/s misspellings would fade out as suggested... and generally they do, with a sharp crossover between 1780-1820....
The change was about .0300% or less, actually not trivial compared to some other changes you can observe over time. I assume that research done with the tool might eventually be used to provide feedback for fixing some of the OCR, assuming, ie, that there are precise fixes.
The tool is a natural for exploring divergences and parallels, and for finding correlations among language, history, and consciousness. Here are some I tried...
[ngrams.googlelabs.com...] (love,hate,fear) - start 1600
[ngrams.googlelabs.com...] (money,happiness,freedom) - start 1700
[ngrams.googlelabs.com...] (Bach,Mozart,Beethoven) - start 1700
[ngrams.googlelabs.com...] (dragons,reptiles) - start 1600
[ngrams.googlelabs.com...] (faith,science) - start 1600
[ngrams.googlelabs.com...] (hot,cold) - start 1700