LANTERNS in ARCHITECTURE
Lanterns were identified as a distinctive architectural feature as openings during Romanesque period. The Lantern developed from many preceding elements that were placed atop a building. These elements, in different cultures, served Three main purposes 1 Bringing in daylight into the interiors of buildings, 2 Provide a glowing feature in the otherwise dark exterior scape, and, 3 Add aeriform silhouettes to the building.
Clerestory openings were forerunners of the lantern lights. These were horizontal slit openings created by keeping the aisle slab at lower level, than the main slab. The clerestory openings provided a consistent quality of light to the interior space. Egyptian and Mycenaean architecture used upper level openings for lighting and ventilation of large rooms. In Minoan palaces of Crete such as Knossos, light-wells were used to supplement the daytime illumination. In Roman basilicas, it formed a series of windows in the upper part of the main hall.
Series of windows in flat side walls of Roman Basilicas provided sufficient, though highly directional illumination. In the Romanesque period the central section became much larger (the four corners of the holy Cross-based plan). Use of pendentives allowed placement of a circular dome or a square form. The dome sitting in this manner, however, was not perceptible from outside, so was raised with the addition of a drum. The drum was pierced with several windows (Santa Hagia, Constantinople). The square space in a plan, with a mounted dome provided a wonderful aeriform, but had two basic issues. It had no clear direction for prayers and related ceremonies and it was very costly, time and material consuming system.
In Romanesque and Gothic churches, the section over the aisles had several clerestory windows. These windows, over the ages, became taller and extent wise much larger. The larger windows created wonderful day-lit bright interiors, but robbed the charm of upper-level clerestory openings.
Gothic architecture afforded several stratified openings, and the need for intense daylight illumination was replaced by some dramatic local effects. This was done with use of light towers. Tower structures, were used for bells (campanile or belfry), stairs, and as architectural elements (spire, steeple). The towers are nominally solid structures at the base but as they rise, have progressively larger size or greater number of openings.
The tower transmitted light with even, but dramatic effect like a modern day spot light. Spires and steeples became very tall pointed structures, almost reaching the sky. These were visible from a distance, but became useless for transmitting light to the interiors. These became light-houses because lit by a small oil lamp, and its presence and forms were perceptible in the dark nights.
Spires and Steeple like spear structures, marked their presence by changing the silhouette of the building. Several of them were added to satisfy multiple sponsors. The structures had to be light weight and properly framed to reach the skies. These were wood-framed, but later sheet metals (18C) began to be used. During the Victorian era and later large nonreligious public buildings and large residences began to use the tower like structures. These were used as decorative roofing element and for as light-well for stairs. At places the need to add silhouette undulation was not acute and elaborate skylights, cupolas, and glass conservatories were used.
In Indian architecture of Mughal period, Roof Chhatris (pavilions) were placed on building terraces, gates, ramparts, etc. Chhatris were functional summer seats on terraces and also decorative forms.