"A week later," she continued, "we went to London and there saw a good deal of our next-door neighbours. Madame was on terms of the closest intimacy with them, and frequently we would dine there, or they would dine with us, while one evening Hartmann--who did not live there, but only came to continue his scientific studies, assisted by Mr. Kerr, who took the keenest interest in them--invited us up into his laboratory, and after showing us Mr. Kerr's collection of pet Indian snakes, which I confess I did not appreciate, he exhibited to us an experiment which he told us had never been successfully accomplished by any other man except himself, namely, the liquefaction of hydrogen. To succeed in this, he told us, all his efforts had been directed for years, and now that he had successfully solved the problem he would one day launch it upon the scientific world as a bolt from the blue. Our friends gave excellent dinners, were evidently possessed of almost unlimited means, and were never so happy as when the Blains and ourselves were at their table or playing cards with them. Soon, however, another matter caused me deep reflection. One evening at The Hollies, after the Blains and Hartmann had been closely closeted with Madame, discussing, as they so often did, their private affairs, I found lying beneath a book upon the table, and apparently overlooked, several plain cards, and others with devices, lines and circles roughly-drawn in ink. Then two or three days later, when I chanced to call in at the Kerrs, I noticed, stuck behind a mirror over the mantelshelf, some cards exactly similar. I was alone, therefore my curiosity prompted me to examine them. Upon them I found exactly similar devices!" "Ah! what connexion had those cards with the affair?" interrupted Dick.