October 1865 Gilbert's improved Fire Alarum
It was a dangerous place to be, Victorian England. With many industrial practices in their infancy deadly boiler explosions, fatal fires and assorted other unpleasant accidents were commonplace — and regularly reported by early issues of The Engineer.
It was into this world of fire and pain that Mr Gilbert introduced his Fire Alarum, an elegant reminder in today's age of plug and play sensors, that Engineers once had only mechanical means at their disposal.
Gilbert's device, a fore-runner to modern fire alarm systems, had at its heart a 'a fusible wire or cord'. This wire, claimed the article, could be used to connect 'several rooms of a house, parts of a ship or other place and attached to a suitable alarum, in such a manner as, when acted upon by heat, it will be dissolved or melted'.
The article explained that the device would be wound up rather like an alarm clock and when high temperatures caused the fusible wire to melt a system of cogs and pulleys would be set in motion, which would cause a hammer to repeatedly strike a bell and raise the alarm.
This fuse which, according to the article, would melt at temperatures of between 90ºF and 120ºF is made from an exotic recipe: 'gutta-percha 16 parts, chloride and sulphur two parts, sulphuret of antimony three parts and cooper bronze one part.'
Gilbert envisages an application of the system that would surely have had Victorian plumbers puffing out their cheeks saying 'it's going to cost you guv'.
'In applying this invention to several rooms of a house one method would be to convey a wire from the lever through the pulley, along passages, mouldings, cornices, floors, ceilings, above or below ground, in any convenient manner, by cranks, joints or pulleys and in each room or other place introduce short lengths of the fusible wire, so that the heat of any room through which the wire passes rising to a temperature sufficient to dissolve or melt the same, the continuous line would be broken and liberate the lever… which will allow the hammer to strike the bell.'