with other scientific activities. Behind the man of science with his outfit of knowledge is the indispensable mechanic with his outfit of manual skill.
Thorndyke's laboratory assistant, Polton, was a fine example of the latter type, deft, resourceful, ingenious and untiring. He was somewhat of an inventive genius, too; and it was one of his inventions that connected us with the singular case that I am about to record.
Though by trade a watchmaker, Polton was, by choice, an optician. Optical apparatus was the passion of his life; and when, one day, he produced for our inspection an improved prism for increasing the efficiency of gas-buoys, Thorndyke at once brought the invention to the notice of a friend at the Trinity House.
As a consequence, we three—Thorndyke, Polton and I—found ourselves early on a fine July morning making our way down Middle Temple Lane bound for the Temple Pier. A small oil-launch lay alongside the pontoon, and, as we made our appearance, a red-faced, white-whiskered gentleman stood up in the cockpit.
"Here's a delightful morning, doctor," he sang out in a fine, brassy, resonant, sea-faring voice; "sort of day for a trip to the lower river, hey? Hallo, Polton! Coming down to take the bread out of our mouths, are you? Ha, ha!" The
