This week in 1871
Illuminating the enemy
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The ground light ball was one of the earliest military methods of casting light on an enemy’s position at night. It faced a number of challenges, including inaccurate positioning and flimsy construction.
The ball was usually made up of an inflammable short cylinder placed within a frame of hoop iron. A mixture of sulphur, saltpetre, resin and linseed oil was placed in canvas and wrapped around the cylinder.
In an article written in 1871, The Engineer was critical of its design. ‘Its elongated form is quite unsuited to smooth-bored ordnance. It is fragile and can only bear a small firing charge. The composition is by no means the one that gives the most brilliant light.’
In 1850, General Boxer attempted to address these problems by introducing a light ball attached to a parachute. The design consisted of two outer and two inner hemispheres of tinned iron. A fuse triggered a bursting charge, igniting the mixture within while a parachute controlled the rate of descent.
Despite being more accurate, the parachute light ball could only burn for two and a half minutes, while the ground light ball lasted for an average of sixteen minutes.
The Engineer highlighted a more innovative approach developed by M. V. Serrin and being trialled in Chatham in 1871. The system involved the use of a parabolic mirror made of silvered copper through which two points of electric light were reflected.
‘It is stated that on one occasion a very curious, and at first unaccountable effect, was produced by the reflection of the light from the eyes of a number of sheep in the vicinity,’ said the article. ‘To be really efficient, a number of the light reflectors should be used…more extended trials should be made in this interesting matter.’
