[Great Lighthouses of Ireland]
1. The First Lighthouses
Before the development of clearly defined ports, mariners were guided by fires built on hilltops. Since raising the fire would improve the visibility, placing the fire on a platform became a practice that led to the development of the lighthouse. Originally, lighthouses functioned more as an entrance marker to ports than as a warning signal for hidden dangers.
The most famous lighthouse structure from antiquity was the Pharos of Alexandria built in the third century BC, one of the seven wonders of the ancient world. It stood more than 350 feet tall until an earthquake destroyed it in the 1300s.
2. The Statue of Liberty functioned as a lighthouse for 16 years until 1902. It could be seen from 24 miles away.
3. Lighthouse Lunacy
The Fresnel lamps in lighthouses floated on baths of mercury (weighing about 1½ tons), which kept the lamp perfectly level and allowed it to turn without friction.
Mercury vapour is associated with such effects as short-term memory loss, confusion, and the manic behaviour we associate with ‘mad hatters’, so it may be that the psychological difficulties sometimes reported amongst lighthouse keepers were caused (or at least exacerbated) by mercury poisoning.” [qi.com]
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