夢溪筆談（選）梦溪笔谈（选）

陽燧照物皆倒，中間有礙故也。算家謂之「格術」。如人搖艣，臬為之礙故也。若鳶飛空中，其景隨鳶而移，或中間為窻隙所束，則影與鳶遂相違，鳶東則影西，鳶西則影東。又如窻隙中樓塔之影，中間為窻所束，亦皆倒垂，與陽燧一也。陽燧面窪，以一指迫而照之則正；漸遠則無所見；過此遂倒。其無所見處，正如窗隙、櫓臬、腰鼓礙之，本末相格，遂成搖櫓之勢。故舉手則影愈下，下手則影愈上，此其可見。陽燧面窪，向日照之，光皆聚向內。離鏡一、二寸，光聚為一點，大如麻菽，著物則火發，此則腰鼓最細處也。豈特物為然，人亦如是，中間不為物礙者鮮矣。小則利害相易，是非相反；大則以己為物，以物為己。不求去礙，而欲見不顛倒，難矣哉！《酉陽雜俎》謂「海翻則塔影倒」，此妄說也。影入窗隙則倒，乃其常理。

阳燧照物皆倒，中间有碍故也。算家谓之「格术」。如人摇橹，臬为之碍故也。若鸢飞空中，其景随鸢而移，或中间为窗隙所束，则影与鸢遂相违，鸢东则影西，鸢西则影东。又如窗隙中楼塔之影，中间为窗所束，亦皆倒垂，与阳燧一也。阳燧面洼，以一指迫而照之则正；渐远则无所见；过此遂倒。其无所见处，正如窗隙、橹臬、腰鼓碍之，本末相格，遂成摇橹之势。故举手则影愈下，下手则影愈上，此其可见。阳燧面洼，向日照之，光皆聚向内。离镜一、二寸，光聚为一点，大如麻菽，著物则火发，此则腰鼓最细处也。岂特物为然，人亦如是，中间不为物碍者鲜矣。小则利害相易，是非相反；大则以己为物，以物为己。不求去碍，而欲见不颠倒，难矣哉！《酉阳杂俎》谓「海翻则塔影倒」，此妄说也。影入窗隙则倒，乃其常理。

A burning mirror shows things upside down, because something stands in the way in between. The mathematicians call this the art of crossing. It is like a man sculling a boat, where the oarlock stands in the way. When a kite flies in the sky its shadow moves with it; but if, in between, the light is pinched by a crack in a window, the shadow and the kite go opposite ways: when the kite goes east the shadow goes west, and when the kite goes west the shadow goes east. Again, the shadow of a tower coming through a crack in a window is pinched by the window and hangs upside down, just as in the burning mirror. The face of a burning mirror is hollow. Hold a finger close to it and the image is upright; move the finger slowly away and nothing can be seen; beyond that the image is inverted. The place where nothing can be seen is like the window crack, the oarlock, or the waist of an hourglass drum: the two ends cross there, and so the image moves like a scull. That is why, when you raise your hand, the image goes lower, and when you lower your hand, the image goes higher; this can be seen for oneself. When the hollow face of the burning mirror is turned to the sun, the light all gathers inward. An inch or two from the mirror it gathers into a single point the size of a hemp seed or a bean, and when it touches something, fire breaks out; this is the narrowest part of the hourglass drum. And it is not only things that are like this; people are the same. Few have nothing standing in the way in between. In small matters, gain and harm change places and right and wrong are reversed; in large matters, people take the self for the other and the other for the self. If one does not try to remove what stands in the way, and still hopes to see things the right way up, that is hard indeed. The Youyang Zazu says that when the sea turns over, the reflection of a pagoda is upside down; this is idle talk. An image that passes through a crack in a window is inverted; that is the ordinary principle.

又問予以「日月之形，如丸邪？如扇也？若如丸，則其相遇豈不相礙？」余對曰：「日月之形如丸。何以知之？以月盈虧可驗也。月本無光，猶銀丸，日耀之乃光耳。光之初生，日在其傍，故光側而所見才如鉤；日漸遠，則斜照，而光稍滿。如一彈丸，以粉塗其半，側視之，則粉處如鉤；對視之，則正圓，此有以知其如丸也。日、月，氣也，有形而無質，故相直而無礙。」

又问予以「日月之形，如丸邪？如扇也？若如丸，则其相遇岂不相碍？」余对曰：「日月之形如丸。何以知之？以月盈亏可验也。月本无光，犹银丸，日耀之乃光耳。光之初生，日在其傍，故光侧而所见才如钩；日渐远，则斜照，而光稍满。如一弹丸，以粉涂其半，侧视之，则粉处如钩；对视之，则正圆，此有以知其如丸也。日、月，气也，有形而无质，故相直而无碍。」

He also asked me: “Are the sun and moon shaped like balls, or like fans? If they are like balls, would they not get in each other's way when they meet?” I answered: “The sun and moon are shaped like balls. How do I know? It can be tested by the waxing and waning of the moon. The moon has no light of its own; it is like a ball of silver, and it shines only when the sun lights it. When its light first appears, the sun is beside it, so the light falls on its side and what we see is only like a hook. As the sun moves farther away it shines on it more and more obliquely, and the light gradually fills out. Take a pellet and coat half of it with powder: seen from the side, the powdered part looks like a hook; seen face on, it is perfectly round. By this we know the moon is like a ball. The sun and moon are made of qi; they have form but no substance, and so they can stand in line with each other without getting in each other's way.”

世傳虹能入溪澗飲水，信然。熙寧中，余使契丹，至其極北黑水境永安山下卓帳。是時新雨霽，見虹下帳前澗中。余與同職扣澗觀之，虹兩頭皆笄澗中。使人過澗，隔虹對立，相去數丈，中間如隔綃縠。自西望東則見；蓋夕虹也。立澗之東西望，則為日所鑠，都無所覩。久之稍稍正東，踰山而去。次日行一程，又復見之。孫彥先云：「虹，雨中日影也，日照雨即有之。」

世传虹能入溪涧饮水，信然。熙宁中，余使契丹，至其极北黑水境永安山下卓帐。是时新雨霁，见虹下帐前涧中。余与同职扣涧观之，虹两头皆笄涧中。使人过涧，隔虹对立，相去数丈，中间如隔绡縠。自西望东则见；盖夕虹也。立涧之东西望，则为日所铄，都无所睹。久之稍稍正东，逾山而去。次日行一程，又复见之。孙彦先云：「虹，雨中日影也，日照雨即有之。」

It is commonly said that a rainbow can come down into a stream and drink, and this is true. In the Xining years I was sent as envoy to the Khitan, and in the far north, in the Black Water country, we pitched our tents at the foot of Yong'an Mountain. The rain had just cleared, and I saw a rainbow come down into the stream in front of the tents. With my fellow envoy I went down to the stream to look, and both ends of the rainbow came down into it. I sent a man across the stream to stand facing us, with the rainbow between us, some tens of feet apart; between us it was as though a curtain of thin silk hung. Looking from west to east we could see it; it was an evening rainbow. Standing on the east side of the stream and looking west, it was washed out by the sun and nothing at all could be seen. After a long while it moved slowly due east and passed over the mountain. The next day, a stage further on, we saw it again. Sun Yanxian says: “A rainbow is the shadow of the sun in rain; whenever the sun shines on rain, there is one.”

鄜、延境內有石油，舊說「高奴縣出脂水」，即此也。生於水際，沙石與泉水相雜，惘惘而出，土人以雉尾甃之，用采入缶中。頗似淳漆，然之如麻，但煙甚濃，所沾幄幕皆黑。余疑其煙可用，試掃其煤以為墨，黑光如漆，松墨不及也，遂大為之，其識文為「延川石液」者是也。此物後必大行於世，自余始為之。蓋石油至多，生於地中無窮，不若松木有時而竭。今齊、魯間松林盡矣，漸至太行、京西、江南，松山大半皆童矣。造煤人蓋未知石煙之利也。石炭煙亦大，墨人衣。余戲為《延州詩》云：「二郎山下雪紛紛，旋卓穹廬學塞人。化盡素衣冬未老，石煙多似洛陽塵。」

鄜、延境内有石油，旧说「高奴县出脂水」，即此也。生于水际，沙石与泉水相杂，惘惘而出，土人以雉尾甃之，用采入缶中。颇似淳漆，然之如麻，但烟甚浓，所沾幄幕皆黑。余疑其烟可用，试扫其煤以为墨，黑光如漆，松墨不及也，遂大为之，其识文为「延川石液」者是也。此物后必大行于世，自余始为之。盖石油至多，生于地中无穷，不若松木有时而竭。今齐、鲁间松林尽矣，渐至太行、京西、江南，松山大半皆童矣。造煤人盖未知石烟之利也。石炭烟亦大，墨人衣。余戏为《延州诗》云：「二郎山下雪纷纷，旋卓穹庐学塞人。化尽素衣冬未老，石烟多似洛阳尘。」

Within the borders of Fu and Yan there is rock oil; the old saying that “Gaonu county gives out a fatty water” refers to this. It comes up at the water's edge, mixed with sand, stones and spring water, seeping slowly out, and the local people gather it with pheasant tail feathers and put it into jars. It looks very like pure lacquer and burns like hemp, but its smoke is very thick, and the tent curtains it touches all turn black. I suspected that this smoke might be of use, and tried sweeping up the soot to make ink. The ink was black and glossy like lacquer, better than pine-soot ink, so I made a great deal of it; the ink stamped “Yanchuan stone liquid” is this. This thing will surely come into wide use in the world, and I was the first to make ink of it. For rock oil is very plentiful and is produced in the earth without end, unlike pine wood, which in time runs out. Already the pine forests between Qi and Lu are gone, and little by little, in the Taihang, west of the capital and south of the river, most of the pine hills have become bare. The makers of soot do not yet know the advantage of rock smoke. The smoke of coal is also heavy, and blackens people's clothes. I once wrote, in jest, a “Poem of Yanzhou”: “Below Erlang Mountain the snow falls thick; / I pitch a felt tent and live like the men of the border. / Our white robes are all turned black, though winter is not yet old: / the smoke of stone is as thick as the dust of Luoyang.”

余奉使河北，邊太行而北，山崖之間，往往銜螺蚌殼及石子如鳥卵者，橫亙石壁如帶。此乃昔之海濱，今東距海已近千里。所謂大陸者，皆濁泥所湮耳。堯殛鯀於羽山，舊說在東海中，今乃在平陸。凡大河、漳水、滹沱、涿水、桑乾之類，悉是濁流。今關、陝以西，水行地中，不減百餘尺，其泥歳東流，為大陸之土，此理必然。

余奉使河北，边太行而北，山崖之间，往往衔螺蚌壳及石子如鸟卵者，横亘石壁如带。此乃昔之海滨，今东距海已近千里。所谓大陆者，皆浊泥所湮耳。尧殛鲧于羽山，旧说在东海中，今乃在平陆。凡大河、漳水、滹沱、涿水、桑干之类，悉是浊流。今关、陕以西，水行地中，不减百余尺，其泥岁东流，为大陆之土，此理必然。

I was sent on a mission to Hebei, and travelling north along the Taihang mountains I often saw, in the cliffs, the shells of snails and clams, and pebbles like birds' eggs, running across the rock face like a belt. This was once a seashore, though it now lies nearly a thousand li west of the sea. What is called the great plain was all laid down by muddy silt. Yao is said to have banished Gun to Yu Mountain, which the old accounts placed in the Eastern Sea; now it stands on dry level land. The Yellow River, the Zhang, the Hutuo, the Zhuo, the Sanggan and rivers like them are all muddy streams. West of the passes in Shaanxi today, the rivers run in channels no less than a hundred feet below the land, and year after year their mud flows east and becomes the soil of the great plain. This must be the principle of it.

方家以磁石磨針鋒，則能指南，然常微偏東，不全南也，水浮多蕩搖。指爪及碗唇上皆可為之，運轉尤速，但堅滑易墜，不若縷懸為最善。其法取新纊中獨繭縷，以芥子許蠟，綴於針腰，無風處懸之，則針常指南。其中有磨而指北者。余家指南、北者皆有之。磁石之指南，猶柏之指西，莫可原其理。

方家以磁石磨针锋，则能指南，然常微偏东，不全南也，水浮多荡摇。指爪及碗唇上皆可为之，运转尤速，但坚滑易坠，不若缕悬为最善。其法取新纩中独茧缕，以芥子许蜡，缀于针腰，无风处悬之，则针常指南。其中有磨而指北者。余家指南、北者皆有之。磁石之指南，犹柏之指西，莫可原其理。

The masters of techniques rub the point of a needle with a lodestone, and then it can point south; but it always inclines slightly to the east and does not point due south. Floated on water it tends to wobble. It can be balanced on a fingernail or on the rim of a bowl, where it turns even more freely, but these are hard and slippery and it easily falls off. Best of all is to hang it from a thread. The method is to take a single silk filament from new floss and fix it to the middle of the needle with a piece of wax the size of a mustard seed; hang it where there is no wind, and the needle will always point south. Among such needles there are some that, after rubbing, point north. In my household there are both kinds, south-pointing and north-pointing. That the lodestone points south is like the cypress pointing west; no one can trace the reason for it.