Sandbanks are a hazard to marine traffic. Often found near coastlines, near the mouth of a river and around ports, these shallow, submerged beds of sand keep changing their shape and position posing great navigation risk to ships. Because the sand tends to drift with the tides, it is difficult to anchor a warning lightship on a sandbank, much less get a firm foundation for a permanent lighthouse.
The problem of erecting a lighthouse on sandbanks and shoals greatly disturbed Alexander Mitchell (1780 – 1868), an Irish brick-maker who ran a successful brick-making business near Belfast. Belfast has a strong seafaring tradition, and Mitchell had no doubt heard many tragic tales of lives lost at sea and ships grounded on the mudflats. Mitchell decided to do something about it despite having no formal training in engineering, or lighthouse building. Remarkably, Alexander Mitchell was also blind.
Thomas Point Shoal Lighthouse in the Chesapeake Bay, Maryland, United States, was erected in 1875 and still stands today. Photo credit: Mark/Flickr