The UK Intellectual Property Office (IPO) has made available at the British Library, London PDFs of British patent specifications from 1617 to 1899 via a server located there. It is best to visit its Business & IP Centre to see them (and remember a pass is needed for entry to the library).
They are only accessible by asking for specific patent numbers rather than by using e.g. name, address, occupation or title. It is nevertheless a big advance on having to order paper copies and wait for them to be delivered. The entire specification loads very rapidly as a single PDF.
It also means that the paper copies at the IPO will be conserved from damage when requests for copies come in, besides the paper copies at the British Library.
I think it a shame it is not available elsewhere, such as at the patent libraries in the UK, or on the Web for anyone to use. Better still, it would have been good to have it added to the Espacenet database. There are precedents for having patents available only by using the patent number, such as early American and German patents.
At present Espacenet allows British patents to be requested from mid 1893. They can be ordered by patent number or by asking for GB in the publication number field and then by various other fields such as title and name.