Every square of this kind of smallpox is a well, which is decorated with patterns, carvings and colorful paintings, hence the name algae well. Smallpox is a component covering the top of a building, and the dome-shaped smallpox in the building is called "algae well". Caisson is usually located in the upper part of the room, umbrella-shaped, supported by exquisite arches, symbolizing the sublimity of the sky. Caisson is generally painted with colorful paintings and reliefs.
The forms of algae wells are omni-directional and circular. , and the structure is complex. Some algae wells use bucket arches between layers, which are beautifully carved, gorgeous and decorative; Some caissons don't need a bucket arch, but are stacked with wooden boards, which are both beautiful and simple.
The word "algae well" was first seen in Han Fu. Many algae wells in Qing dynasty were decorated with dragon patterns, so they were also called "Longjing". In addition, Shen Kuo's "Meng Qian Bi Tan Qi" recorded some aliases of algae wells: "The ancients called it Qi Jing, also known as algae wells, also known as Gaihai."
The moral of caisson is fire prevention.
Drilling wells at the top of halls and pavilions and decorating them with algae and aquatic plants such as lotus, water chestnut and lotus root are all in the hope of suppressing the fire demon.
Since the discovery of fire, people have also learned about the harm of fire. In order to survive and develop, people have learned to avoid harm. However, due to the low productivity at that time, people still lacked effective means to subdue natural disasters, so they could only try to express their wishes in various ways. The special treatment of caissons by palaces and pavilions belongs to this category. Although idealistic, it also reflects the ancient people's good wishes for fire prevention.