Can we trust the ATCL database?

I’ve been enthusiastic about the database behind the At the Circulating Library website ever since I discovered it nigh on three years ago. Troy Bassett, its creator, deserves much respect and lots of credit both for the work put into creating it and maintaining it, and for his generous open minded policy of making the data itself freely available in snapshot form for nerds like me to play with. I think of the ATCL as the nearest thing we are ever likely to get to an authoritative catalogue of the 19th century novel, and use it as such in other work which I’ll report on later. But (you guessed there was going to be a but) just how reliable is its coverage? Does it cover each decade of the 19th century equally well, or are there gaps?

When asked, Troy assures me that he’s fully aware that there are gaps. He estimates that the true size of the database should be well over 25,000 titles, rather than its current 18,000. He and his team are slowly and meticulously filling the gaps, by hoovering up and checking data from resources such as published catalogues and bibliographies, or online collections like Proquest’s NSTC. It’s tedious and fiddly work, ideally suited to a small farm of graduate students, should you have such a resource at your disposal.

My interest in ATCL is to use it as a reference point when assessing the coverage of other resources, in particular the catalogues of digital libraries. Take, for example, the current Hathi Trust catalogue. This lists 17,433,331 titled volumes in all; 235,035 of them being volumes published in the UK between 1800 and 1900. Removing obvious duplicates (Hathi catalogues each volume of a three-decker separately, usually though not always) brings this down to an only slightly more manageable 129,817 titles. How good is its coverage of 19th century novels? The difficulty of course is to winnow out just the entries which are novels. As I suggested on my blog back in June 2018, the word “novel” in a title turns out to be a very good indicator (other good words include « or » and « tale », « history » etc), so I extracted from the HT records just those titles containing the word “novel” for further investigation: there are 953 of them.

In my earlier work, I’d just assumed that if a title in HT didn’t appear in ATCL then it wasn’t a novel. But how complete is ATCL? A good way of finding out might be to work the other way round: first get a list of things which are definitely (probably) novels — and then check to see whether  they also appear in ATCL.

On my first pass, 284 of my 953 « novels » (i.e. titles containing that word) did not appear in ATCL, which surprised me. But this was mostly a result of my matching procedure being insufficiently robust to cope with the amount of variation in cataloguing practice within the HT records and their occasional divergence from ATCL practice. I spent a happy day or two going through the list of delinquents by hand, taking the opportunity to discard 19th c. reprints of earlier works, translations from other languages (mostly scandalous Zola), and a handful which were clearly not novels at all (e.g. “Photographic amusements : including a description of a number of novel effects obtainable with the camera / by Walter E. Woodbury.”) – all of which brought the number down to 191. I then fixed the “magic keys” used to identify each title in ATCL as necessary, all of which brought me to a manageable 40 titles apparently missing from ATCL, with which to torment Troy Bassett and his team. 40 titles missing from a sample of 953 is pretty good; even 191 missing is not so bad in this always very approximate work. I remain persuaded that the ATCL is a reliable approximation to a representative sampling of the 19th century novel.

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