Criteria for the Placement and Characteristics of Coastal Lighthouses

In addition to site prominence, the kind of light must be carefully selected. The text underscores that revolving lights, which are inherently more powerful than fixed lights, are particularly suitable for outpost positions along the coast. Conversely, it advises that identical lights should not be placed too closely together; ideally, lights that share the same character and appearance should not be located within 100 miles of each other to avoid confusion among mariners^[1]. Moreover, the text cautions against the indiscriminate use of colored media, suggesting that such distinctions in color should only be applied when absolutely necessary, as overuse may compromise the distinctiveness of each light.

Another vital aspect is the elevation of the light, which directly affects its range of visibility. Guidelines mentioned in the source recommend that the elevation for sea-lights should not exceed 200 feet, with about 150 feet being sufficient to meet most navigational needs. It is noted that while lights placed on high headlands are exposed to frequent fog, which can reduce effectiveness, placing them too low might not provide the required visibility. The balance, therefore, involves weighing the risk of fog against the advantage provided by an increased range of light, with the final decision being made based on careful local assessments^[1].

The purpose of coastal lighthouses extends beyond simply providing a navigational aid; they also help in distinguishing one location from another along a coastline. The text emphasizes that for vessels traversing open seas, the placement of lights is instrumental in aiding navigation. For instance, lights meant to guard against hazards like reefs or shoals should be sited as far seaward as possible in order to provide early warning to seamen. In narrow seas, where the range of visibility is naturally limited, fixed lights (or sometimes less powerful ones) may be adequate and may be placed closer together than is advisable on open coasts^[1].

Economic factors also play a significant role in guiding lighthouse placement. The text advises that concerns over initial construction costs should not compromise the selection of the ideal site. Instead, if funds are insufficient, it is better to delay building the lighthouse until an adequate sum can be raised to secure the best possible location. This approach highlights a long-term view in economic planning, ensuring that safety and efficient navigation take precedence over immediate cost savings. Furthermore, from an operational point of view, fewer lighthouses are considered preferable to prevent confusion for mariners, as every additional light may reduce the distinctiveness needed for effective guidance along the coast^[1].

The arrangement of lighthouses must also consider their role in guiding ships not only along open coasts but also into harbors. The report explains that the best position for a sea-light should not be compromised for the sake of a nearby port's short-term benefit. In many cases, a seaward light will serve as a beacon while supplementary lights can be added to lead vessels into the entrance of a port if needed. This strategy ensures that the requirements of both open-sea navigation and local harbor guidance are met efficiently, without overlapping functions that might lead to operational confusion^[1].

Additional factors outlined in the text include the following considerations: (a) The physical characteristics of the coast itself can influence the efficiency of a lighthouse; for example, coastal configurations that are subject to extreme weather may require alternative designs even if they are prominent. (b) Distinctions based on the timing of flashes, or the differences between light and dark intervals, are less reliable because they are easily affected by atmospheric changes. Thus, lighthouses should be distinguished primarily by their characteristic appearances rather than by minute timing intervals. (c) In applications such as narrow seas, reduced distances between lighthouses may be acceptable as the range of the lights is inherently shorter. Finally, floating lights are discouraged due to the inherent risk of drifting and inconsistent performance^[1].