<P> While lighthouse buildings differ depending on the location and purpose, they tend to have common components . </P> <P> A light station comprises the lighthouse tower and all outbuildings, such as the keeper's living quarters, fuel house, boathouse, and fog - signaling building . The Lighthouse itself consists of a tower structure supporting the lantern room where the light operates . </P> <P> The lantern room is the glassed - in housing at the top of a lighthouse tower containing the lamp and lens . Its glass storm panes are supported by metal Astragal bars running vertically or diagonally . At the top of the lantern room is a stormproof ventilator designed to remove the smoke of the lamps and the heat that builds in the glass enclosure . A lightning rod and grounding system connected to the metal cupola roof provides a safe conduit for any lightning strikes . </P> <P> Immediately beneath the lantern room is usually a Watch Room or Service Room where fuel and other supplies were kept and where the keeper prepared the lanterns for the night and often stood watch . The clockworks (for rotating the lenses) were also located there . On a lighthouse tower, an open platform called the gallery is often located outside the watch room (called the Main Gallery) or Lantern Room (Lantern Gallery). This was mainly used for cleaning the outside of the windows of the Lantern Room . </P>

What is the chamber at the top of a lighthouse called