History of the Compass 指南针

Si Nan
Compass (zhǐ nán zhēn 指南针) is one of the four great inventions of ancient China. It is a simple instrument for navigational instrument for determining direction relative to the Earth's magnetic poles. It consists of a magnetized pointer (usually marked on the North end) free to align itself with Earth's magnetic field.

Ancient CompassThe earliest compass originally came out during Warring State Period (zhàn guó shí qī 战国时期). It is made of lodestone, with the shape of a soup ladle. It should be put on a glossy chases and kept balance when it is used. And the handle of the ladle will point to the south. People in ancient China called it Si Nan (sī nán 司南). However, because the lodestones are hard to find and they are easy to lost magnetism, what’s more, Si Nan is not convenient to take for its weight, it is not used extensively.

Till the Song Dynasty (sòng cháo 宋朝), Chinese people made Zhinan Fish (zhǐ nán yú 指南鱼), which is more convenient than Si Nan. It just needs a bowl of water, and put the Zhinan Fish on the surface of the water, then it will help you to determine direction. For long-term improvements, people made the steel needle with magnetism by rubbing it on the lodestone. Therefore the needle with magnetism can be regarded as the compass.

The compass was put into use in people’s daily life, military, and manufacturing, especially in navigation. The first person recorded to have used the compass as a navigational aid was Zheng He (zhèng hé 郑和, 1371-1435), from the Yunnan province in China, who made seven ocean voyages between 1405 and 1433.

指南针
      指南针是中国古代四大发明之一。它是用以判别方位的一种简单仪器，主要组成部分是一根装在轴上可以自由转动的磁针。磁针在地磁场作用下能保持在磁子午线的切线方向上。磁针的北极指向地理的北极，利用这一性能可以辨别方向。常用于航海、大地测量、旅行及军事等方面。
指南针的发明是中国劳动人民在长期的实践中对物体磁性认识的结果。由于生产劳动，人们接触了磁铁矿，开始了对磁性质的了解。人们首先发现了磁石引铁的性质。后来又发现了磁石的指向性。经过多方的实验和研究，终于发明了可以实用的指南针。
    
Zhinan Fish      春秋时代，人们用整块天然磁石经过琢磨制成勺型，勺柄指南极，并使整个勺的重心恰好落到勺底的正中，勺置于光滑的地盘之中，地盘外方内圆，四周刻有干支四维，合成二十四向，静止时，勺尾指向南。这就是指南针的雏形——司南。这样的设计是古人认真观察了许多自然界有关磁的现象，积累了大量的知识和经验，经过长期的研究才完成的。司南的出现是人们对磁体指极性认识的实际应用。 但司南也有许多缺陷，天然磁体不易找到，在加工时容易因打击、受热而失磁。所以司南的磁性比较弱，而且它与地盘接触处要非常光滑，否则会因转动摩擦阻力过大，而难于旋转，无法达到预期的指南效果。而且司南有一定的体积和重量，携带很不方便，这可能是司南长期未得到广泛应用的主要原因。

Compass      到了宋代，劳动人民掌握了制造人工磁体的技术，又制造了指南鱼。这种人工传磁方法制成的指南鱼比使用司南方便多了，只要有一碗水，把指南鱼放在水面上就能辨别方向了。经过长期的改进，人们又把钢针在天然磁体上摩擦，钢针也有了磁性。这种经过人工传磁的钢针可以说是正式的指南针了。

      指南针一经发明很快就被应用到军事、生产、日常生活、地形测量等方面，特别是航海上。指南针在航海上的应用有一个逐渐发展过程。成书年代略晚于《梦溪笔谈》的《萍洲可谈》中记有：“舟师识地理，夜则观星，昼则观日，阴晦则观指南针。”这是世界航海史上最早使用指南针的记载。文中指出，当时只在日月星辰见不到的时候才使用指南针，可见指南针刚开始使用时，使用还不熟练。二十几年后，许兢的《宣和奉使高丽图经》也有类似的记载：“惟视星斗前迈，若晦冥则用指南浮针，以揆南北。”到了元代，指南针一跃而成海上指航的最重要的仪器了。不论昼夜晴阴都用指南针导航了。而且还编制出使用罗盘导航，在不同航行地点指南针针位的连线图，叫做“针路”。船行到某处，采用何针位方向，一路航线都一一标识明白，作为航行的依据。