Burning Lenses
The danger from Lenses, when the heat of the sun is powerful, is well known. As an illustration, we may relate an instance which occurred on the premises of Messrs. Negretti and Zambra, philosophical instrument makers, in Hatton Garden. There was a smell of fire, but it could nowhere be detected, until a person entered the shop from the street with the startling information that the window was on fire, and such was really the fact: a large reading-lens hanging in the window exposed to the sun, its focus happening to be just within range of the woodwork of the window fittings, set fire to them, and no doubt in a very few seconds some serious damage would have been caused. Is it not possible that in tropical climates, when vessels are becalmed, they may be set on fire by the eye-deck lights everywhere observable on ships’ decks; or, nearer home, in warehouses, &c., where such means of lighting is resorted to? The matter merits serious consideration and should serve as a caution.