'...We know there are some things we do not know. But there are also unknown unknowns – there are things we do not know we don't know.'
---Donald Rumsfeld, US Secretary for Defence, 2002
The famous quote above, not at first glance relevant to genealogy, is applicable to a particular blind spot which may affect researchers as the use of digitised sources online becomes ever more prevalent.
The easy availability of scanned versions of out-of-copyright publications, works often difficult to locate outside the libraries of a few cities, could lead one to the assumption that everything useful that was published before a certain date is now available somewhere on the internet. Of course, sweeping statements are a hazard in any case, but the falsehood of this assumption is particularly acute when considered in the light of the original size of the books scanned.
It seems that most automated book scanning equipment will not accomodate works larger than a certain page size. This is a particularly vexing problem for genealogists, as many early works in the field - such as groundbreaking county histories and volumes of pedigrees - seem to have been printed in the Large Folio size and so a great many of them, even while safely out of copyright by a century or so, have not received the same treatment as contemporary or newer works, simply because of their size. Researchers who may be initially surprised at not locating - through Google books or archive.org - certain pedigrees, charts or antiquarian content, from works legally safe to be freely made available online, should investigate the original size of the publication using reference catalogues; and if it was Octavo or larger, then it's probably pointless to keep searching online - back to the 'Physical' library.
One such work, of great value but not online - nor likely to be in the short term - is George Baker's History and Antiquities of the County of Northampton, a work I recently needed for its pedigree of the Knightley family of Fawsley, which turned out to be but one example of the sort of ancient gem one cannot take for granted online. That said, thanks to my digital camera, I am happy to remedy the Internet's deficiency in this regard, and hope others may also find the below pedigree useful in due course!