Common, and home by another route. On one occasion, as he was crossing a stile, he saw that he was watched, and thenceforth he took his walks in the evening, but never along the same road. There were only two occasions on which it is recorded that scientific men were admitted to Cavendish's laboratory. The first was in 1775, when Hunter, Priestley, Romayne, Lane, and Nairne were invited to see the experiments with the artificial torpedo. The second was when his experiment on the formation of nitric acid by electric sparks in air had been unsuccessfully attempted by Van Marum, Lavoisier, and Monge, and he "thought it right to take some measures to authenticate the truth of it." Besides his house at Clapham, Cavendish occupied (by his instruments) a house in Bloomsbury, near the British Museum, while a "mansion" in Dean Street, Soho, was set apart as a library. To this library a number of persons were admitted, who could take out the books on depositing a receipt for them. Cavendish was perfectly methodical in all his actions, and whenever he borrowed one of his own books he duly left the receipt in its place. The only relief to his solitary life was afforded by the meetings of the Royal Society, of which he was elected a Fellow in 1760; by the occasional receptions at the residence of Sir Joseph Banks, P.R.S.; and by his not infrequent dinners with the Royal Society Club at the Crown and Anchor; and he may sometimes have joined the social gatherings of another club which met at the Cat and Bagpipes, in Downing Street. It was to his visits to the Royal Society Club that we are indebted for the only portrait that exists of him. Alexander, the draughtsman to the China Embassy, was bent upon procuring a portrait of Cavendish, and induced a friend to invite him to the club dinner, "where he could easily succeed, by taking his seat near the end of the table, from whence he could sketch the peculiar great-coat of a greyish-green colour, and the remarkable three-cornered hat, invariably worn by Cavendish, and obtain, unobserved, such an outline of the face as, when inserted between the hat and coat, would make, he was quite sure, a full-length portrait that no one could mistake. It was so contrived, and every one who saw it recognized it at once." Another incident is recorded of the Royal Society Club which, perhaps, reflects as much credit upon Cavendish as upon the Society. "One evening we observed a very pretty girl looking out from an upper window on the opposite side of the street, watching the philosophers at dinner. She attracted notice, and one by one we got up and mustered round the window to admire the fair one. Cavendish, who thought we were looking at the moon, hustled up to us in his odd way, and when he saw the real object of our study, turned away with intense disgust, and grunted out, 'Pshaw!'"