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Abstract
Oil lamps are one of the earliest kinds of portable lighting devices which has been used by mankind all over the world, including Iran. Therefore, this essay, while studying on and seeking formal changes and developments of Iranian oil lamps from historical period, aims to explain these developments in terms of a typological classification. In order to achieve this goal, here in this essay, applying descriptive analytical method of research, first I have depicted the different steps and developments of earthenware and bronze oil lamps from very moment of their appearance up to the beginning of historical period in Iran. Then in historical period I am going to discuss developments in the shapes and forms of earthenware and bronze oil lamps, respectively. While one can distinguish at least six types of earthenware lamps, metal lamps can be categorized only in three types. There are various factors which has influenced developments on the forms of metal and earthenware lamps. Earthenware lamps, for example, have been influenced both by Iranian bronze lamps and Greek and Roman earthenware lamps. On the contrary, although bronze lamps have an original design and compared to earthenware lamps are less inspired by foreign shapes, they have mostly been influenced by their own technological developments. 
Keywords: Iran, Historical Period, , Lighting Devices, Earthenware Oil Lamps, Bronze Oil Lamps

Introduction
Oil lamps are one of the earliest kinds of portable lighting devices which has been used by mankind all over the world, including Iran. These old and archaic lamps use vegetal wicks and vegetal or animal oil to produce artificial lighting. It is not so clear when and how the very idea of such a lighting device has been developed in Iran, however it is somehow obvious that the final design and structure of the lamps already has been created and stablished way before the beginning of historical period in Iran. There again, during historical period, one cannot see and determine really distinctive changes in the old-stablished function of these oil lamps, but their shapes and forms has been gone through many changes and developments. Therefore, this essay, while studying on and seeking formal changes and developments of Iranian oil lamps from historical period, aims to explain these developments in terms of a typological classification. In order to achieve this goal, here in this essay, applying descriptive analytical method of research, first I have depicted the different steps and developments of earthenware and bronze oil lamps from very moment of their appearance up to the beginning of historical period in Iran. Then in historical period I am going to discuss developments in the shapes and forms of earthenware and bronze oil lamps, respectively. These developments unlike prehistorical developments of the lamps are obvious and tangible. 

Disscussion
Therefore, one can categorize almost easily the evolution of forms of earthenware lamps in six major types. The first type of earthenware oil lamps is that of bowl like shapes. These have a simple body with a small protruding part on its rim as wick holder. Second type is consisted of oil lamps with boat shaped bodies. These lamps differ from previous ones only in their slightly bigger wick holders and bodies of somehow oval form. earthenware oil lamps of third type have completely round wheel-made bodies with small round-shaped wick holders which has been totally separated from their bodies. Oil lamps of the next type can be distinguished from previous types mainly based on their mold-produced bodies. Dome shaped bodies without distinctive wick holders are basic characteristics of oil lamps of fifth type. And finally, the sixth type of earthenware oil lamps is characterized by closed and tubular wick holders continuing the form of their bodies. On the other hand, it is possible to make at least three groups out of bronze oil lamps of this period. The first group contains oil lamps of closed bodies with elongated tubular wick holders. Oil lamps of second group have spherical bodies and separated small wick holders. And zoomorphic oil lamps make third group of this bronze Iranian vessels from historical period. Although variety in forms of earthenware oil lamps is very considerable, the forms of some of them has been developed under direct influences of foreign earthenware oil lamps or Iranian bronze lamps. On the contrary, most of the oil lamps made of bronze have original forms and designs. According to author’s observations, it can be concluded that the main factors behind the developments and changes in designs and forms of both earthenware and bronze oil lamps include: the very first prototype of oil lamps, technological factors, inter medium factors, cross medium factors, foreign factors. 

Conclusion
The main idea of mechanism of a lighting device called oil lamp has been conceived most probably during prehistorical times. However, during historical period, due to rapid improvement of technologies, especially those of metalworking and earthenware production, numerous developments and changes has occurred in regard to forms and shapes of oil lamps. These changes in the forms of earthenware lamps are considerable. While one can distinguish at least six types of earthenware lamps, metal lamps can be categorized only in three types. There are various factors which has influenced developments on the forms of metal and earthenware lamps. Earthenware lamps, for example, have been influenced both by Iranian bronze lamps and Greek and Roman earthenware lamps. On the contrary, although bronze lamps have an original design and compared to earthenware lamps are less inspired by foreign shapes, they have mostly been influenced by their own technological developments.