A good instance is thus narrated by Sir Frederick Arrow. "When the electric light was first exhibited permanently at Dungeness, on 6th June, 1862, a committee of the Elder Brethren, of which I was one, accompanied Faraday to observe it. We dined, I think, at Dover, and embarked in the yacht from there, and were out for some hours watching it, to Faraday's great delight--(a very fine night)--and especially we did so from the Varne lightship, about equidistant between it and the French light of Grisnez, using all our best glasses and photometers to ascertain the relative value of the lights: and this brings me to my story. Before we left Dover, Faraday, with his usual bright smile, in great glee showed me a little common paper box, and said, 'I must take care of this; it's my special photometer,'--and then, opening it, produced a lady's ordinary black shawl-pin,--jet, or imitation perhaps,--and then holding it a little way off the candle, showed me the image very distinct; and then, putting it a little further off, placed another candle near it, and the relative distance was shown by the size of the image. He lent me this afterwards when we were at the Varne lightship, and it acted admirably; and ever since I have used one as a very convenient mode of observing, and I never do so but I think of that night and dear good Faraday, and his genial happy way of showing how even common things may be made useful." After this Faraday modified his glass-bead photometer, and he might be seen comparing the relative intensity of two lights by watching their luminous images on a bead of black glass, which he had threaded on a string, and was twirling round so as to resolve the brilliant points into circles of fainter light; or he fixed the black glass balls on pieces of cork, and, attaching them to a little wheel, set them spinning for the same purpose. Some of these beads are preserved by the Trinity House, with other treasures of a like kind, including a flat piece of solder of an irregular oval form, turned up at one side so as to form a thumb-rest, and which served the philosopher as a candlestick to support the wax-light that he used as a standard. The museum of the Royal Institution contains a most instructive collection of his experimental apparatus, including the common electrical machine which he made while still an apprentice at Riebau's, and the ring of soft iron, with its twisted coils of wire isolated by calico and tied with common string, by means of which he first obtained electrical effects from a magnet.