Chapter 15 Section 3 "Five Sacred Mountains" and the Application of Contour Lines

Scholars who study the history of Chinese science and technology found a "True Shape Map of Dongyue (Mount Tai)" in a "True Shape Map of the Five Sacred Mountains" published in the 17th century. towards.When they compared this map with the current Mount Tai map represented by contour lines, they found that it was roughly the same (Fig. 12).According to the description of "Five Sacred Mountains", the original picture was made by people in the Tang Dynasty, and it has been lost long ago, and the author is no longer available.However, some clues can be found in the "Inner Biography of Emperor Wu of the Han Dynasty" written by Ge Hong in the Western Jin Dynasty:

The emperor also saw that there was a volume of books in the Queen Mother's towel collection, which was contained in a purple brocade bag.The emperor asked if this book is a celestial spirit, can we look forward to it if we don't examine it?The queen mother came out to show it and said: "This picture of the true shape of the five mountains...is it suitable for your filthy quality?..." The emperor kowtowed to the ground, and he was very pleased.The Queen Mother said: "...it is because of the rules of the source of the mountain. Seeing the twists and turns of the rivers and mountains, the mausoleum turns around, the mountains are high and long, and the circle is winding. Xuantai, it comes out as a letter of spiritual truth. All immortals wear it like a seal; Taoist priests hold it, and travel through mountains and rivers. Hundreds of gods and spirits respect and get close..."

[Translated today] Emperor Wu of the Han Dynasty saw a volume of books in the queen mother's small box, which was placed in a purple brocade bag.He asked if it was a prescription for immortality, and wondered if he could have a look.The Queen Mother took it out to him and said, "This is the true shape of the Five Sacred Mountains... how can an ordinary person like you have the right to carry it with you?" Emperor Wu knelt on the ground and kowtowed, begging again and again.The Queen Mother said: "...then using a compass and a ruler, the upper reaches of the river were measured, and the outlines of the mountains were drawn with twisted lines. The direction of the mountains will be reversed, and the direction of the hills will change. The slope is described with complex curves, just like written characters. Therefore, the name of the mountain is determined according to its natural shape, and the true shape of the mountain is hidden in these characters. The symbols of the mountain shape are hidden in the mysterious In Taichung, taking it out is a token of supernatural powers. Immortals can take it with them to ward off evil spirits, and Taoists can take it to travel safely. Hundreds of gods and immortals cherish and praise it..."

This book is a Taoist classic. Although the content is not credible, it proves that at that time, great attention was paid to the measurement and depiction of geographical elements such as the direction, shape, height, and width of canyons of mountains and peaks. Therefore, the lines and shapes on the map were not arbitrary. product of.If this claim is confirmed, it would be conclusive evidence that China had topographic maps drawn with primitive contour lines before the 10th century.And the lines of the original picture must be more accurate and clear than this picture that may have been reprinted many times.

However, because this is an isolated and indirect evidence, we still cannot explain how people at that time discovered and mastered the method of contour lines to represent the "true shape" of Mount Tai, and it is even more difficult to speculate what instruments they used and how to interpret the measurement results. above.