In ancient times, due to the backwardness of productivity, people's return from input to output was extremely limited. Therefore, the ancients attached great importance to economy in their lives.
Take lighting as an example: the oil lamp used by ordinary people is already very small. From today's perspective, it is far from wasting oil. However, our ancestors are still very dissatisfied and hope to save more. Driven by this idea, someone invented an oil-saving lamp called "clip lamp" in the late Tang Dynasty (Figure 4).
Regarding this kind of lamp, Lu You, a great writer in the Song Dynasty, described it in Volume 10 of Notes on the Old Xuegong: "An Gongji has a poem" Fuel-saving Lighting ",which is found in Han and Jia today. It's easy to open a small mouth at one end and pour cold water into it every night. Ordinary lamps are dried by fire, so they dry quickly. Otherwise, they will save fuel for several and a half hours. When Shao Gong gave alms to Han Jia, he left several Chinese and Korean literati behind. According to Wen 'an, it was also tasted as a jade decree, so Han Jia had this thing for hundreds of years. "
So, this is a kind of lamp with interlayer. Cold water can be injected into the interlayer to form a simple but effective cooling water jacket. It can reduce the fuel temperature, reduce evaporation and achieve the purpose of saving fuel. From Lu You's description, we also know that this fuel-efficient oil lamp is not only loved by ordinary people, but also favored by "literati".
Modern archaeological achievements have confirmed that the provincial oil lamp was invented in the Tang Dynasty and has been unearthed in the excavation of Qiongyao site in the Tang Dynasty in Qionglai County, Sichuan Province. Provincial oil lamps have been popular in various dynasties since the Tang Dynasty and have been used until the Qing Dynasty. The cooling water jacket of early energy-saving lamps was mostly closed, and the water injection port had only one or two small holes. Later, it developed into a simple straight port (Figure 5), and it was much more convenient to inject clean water. In the Song Dynasty, the water jacket inlet of the fuel-saving lamp was made into a very standardized funnel shape. Since the Yuan Dynasty, the upper covers of some water jackets have been removed to form an open double-pool energy-saving lamp, which is more convenient to use. However, the function and structural principle of the oil-saving lamp are almost unchanged from those when it was first invented in the Tang Dynasty. During this period, the age span exceeded 1000 years. It seems that the wisdom of our ancestors made this small oil-saving lamp perfect from the initial invention, so that future generations could never break through it. In my collection, there are some lamps, from the yellow glaze and blue glaze of Qiong Yao in the Tang Dynasty to the black glaze in the Song Dynasty, the blue and white glaze in the Yuan and Ming Dynasties and the oil lamps in various provinces in the Qing Dynasty. One of the oil lamps in Tin Province in Qing Dynasty is only different from its predecessors in material and appearance.
Today, the provincial oil lamp has been eliminated by history. But the method of "cooling water jacket" to reduce the oil temperature has been handed down. In the process of metal heat treatment, reducing the temperature of oil pool is still an effective method.
There is also a long current lamp. Because its lamp is far away from the oil pool when it burns. It can keep the fuel temperature low all the time. I think it can also be called oil lamp saving.
When you think about it carefully, besides saving fuel, saving oil lamps has another advantage, that is, it reduces the air pollution caused by oil and gas evaporation, which can be said to be a small environmental awareness of the ancients. What enlightenment can scientists today get from it?