This is a borderline question, but I'm going to risk posing it.
Cuthbert Edmund Cullis (1875?-1955?) was a somewhat obscure British mathematician whose opus magnum was a multi-volume treatise called Matrices and Determinoids. While his notation is somewhat idiosyncratic, it was a fairly systematic exposition of most(?) of the linear algebra known by the 1920s (heavy on determinants and minors, but also including invariant factors and canonical forms, or at least things looking like them), along with lots of new results. Some of his innovations, I believe, would be of interest even to us modern people: in particular, in the first 200 pages of Volume 3A, he seems to algorithmically construct multi-resultants using multisymmetric polynomials (aka MacMahon symmetric polynomials). I have never seen this done anywhere else.
Question 1. Has Volume 3A ever been digitized?
Question 2. Is the manuscript of Volume 3B available anywhere?
The reason for Question 2 is mostly curiosity, but I have a rather practical reason for Question 1: I'm interested in understanding multi-resultants elementarily and also in applying multisymmetric polynomials. The twist is that I have access to Volume 3A in hardcopy for the rest of this week, but before I leave this library I'd like to know if it's worth scanning the doorstopper (700 pages!) or someone has already done that work.