Besides the light experiments already mentioned, all those on the time-change of p.d. Immediately after starting the arc, and after sudden changes of current, originally formed part of Prof. Ayrton's ill-fated Chicago Paper, which, after being read at the Electrical Congress in 1893, was accidentally burnt in the Secretary's office, whilst awaiting publication. These highly important experiments were not only the first of their kind, but, as far as I know, they still remain unique. Most of the figures in the first chapter, all the experiments and curves that relate to cored carbons in the fourth and fifth, and some of those on hissing in the tenth, also belonged to this Chicago Paper, which was as full of suggestion as it was rich in accomplished work.