A signal fire or beacon is a pre-built pile of fuel on high ground that is lit to carry one agreed message by flame at night or smoke by day, and a chain of them relays that message across distances beyond any voice. It tells every watcher where you are as well as that you are in danger, it can start a grass fire, and it needs a meaning that an ordinary cooking fire or field burn cannot imitate.
Part of Early Warning Systems
A beacon is a prepared stack of fuel on a hill or tower, kept ready to be lit as a visual alarm, and a beacon chain is a series of such stacks, each in sight of the next, passing a message along by relay.
One Message, Seen A Long Way, Seen By Everyone
A beacon can carry one yes-or-no message a long way in a short time. Its weakness is the same as its strength: it is visible to every watcher in line of sight, friendly or not. The camouflage article gives how far light and fire carry at night (Camouflage and Concealment). A beacon announces the position of the signaller and the fact that they are alarmed.
Beacons are for the settlement scale, where a neighbouring post or village has agreed to watch for it. For a single household, a horn, a mirror or a runner does the job with less cost. Codes and relay networks are covered in Signal Systems.
What You Need
- A prepared stack of dry wood, kept under a light roof, with kindling and a way to light it from a banked fire. See Fire Management.
- A hilltop or tower with a view of the next station and the area it guards.
- Watchers at each station, on rota, who know the code.
- An agreed meaning for the signal, tested at least yearly.
- A cleared fire-safe ground around the stack, bare earth or rock, and a means of putting the fire out.
Method: Build, Agree, Relay
Step 1: Fix the stations by line of sight. Check that each beacon can be seen from the next one in daylight and, with a test fire, at night.
Step 2: Keep the stack ready. Dry fuel, covered; a lighter or fire source in a dry box.
Step 3: Agree the meanings. One pattern for “danger”, a different one for “all clear”, and a rule that a lone fire is not an alarm. Two fires, or a smoke by day and a flame by night, are harder to confuse with a cooking fire.
Step 4: Light on a decision, not a feeling. The watcher lights it when the criteria are met, then sends a runner or horn blast to the house.
Step 5: Relay. Each station lights its own on seeing the previous one, and does not wait to be sure.
Step 6: Put it out at the all-clear and check the ground.
Worked Example: How Far Apart And How Fast
Spacing. If both stations are on hills h1 and h2 above the plain between them, the geometric line-of-sight distance on flat ground is d = 3.57 × (√h1 + √h2) km, using the horizon formula for each end with R = 6,371 km as in Observation Posts. For two beacons 50 m above the plain: √50 = 7.07, so d = 3.57 × (7.07 + 7.07) = 3.57 × 14.14 = 50.5 km. That is a ceiling for open, flat country with perfect air, not a spacing. Haze, hills in between and the fire’s own visibility at night cut it, so choose spacing by test.
Speed (example inputs). If each station takes 3 minutes from seeing the previous signal to its own flame, a chain of 10 stations passes the message in 10 × 3 = 30 minutes. A messenger walking 100 km at 5 km/h needs 100 ÷ 5 = 20 hours of walking. The chain is not fast per hop but it keeps going while people sleep, and it needs ten crews on standby.
Common Mistakes
- Lighting on a rumour. A false beacon costs the next stations’ trust.
- A stack left uncovered. Wet fuel does not ignite when you need it.
- A stack beside buildings. Embers start a roof fire.
- A signal with no meaning agreed. The watcher at the next hill sees a fire and does not know what to do.
Safety
Beacons set grassland, woodland and roofs on fire
Light only on bare ground with a cleared ring and water or sand on hand, never in dry wind or a drought, and never leave a beacon burning unattended. Burn only wood, not tyres, plastics or treated timber, whose smoke is poisonous. A beacon on a tower or hill is also a fall and a lightning risk for the watcher; keep a safe way down. Remember that it also marks your position for everyone who can see it.
What’s Next
- Learn next: Mirror and Light Signals — a faster, narrower signal for the sunny hours
- Combine with: Signal Systems — codes, authentication and relay networks