沈括 著

【原文】

《夢溪筆談·卷19器用12》

世有透光鑒，鑒背有銘文，凡二十字，字極古，莫能讀。 以鑒承日光，則背文及二十字，皆透在屋壁上，了了分明。人有原其理，以為鑄時薄處先冷，唯背文上差厚，后冷而銅縮多。文雖在背，而鑒面隱然有跡，所以于光中現(xiàn)。予觀之，理誠如 ?是。然予家有三鑒，又見他家所藏，皆是一樣，文畫銘字無纖異者，形制甚古。唯此一樣光透，其他鑒雖至薄者皆莫能透。 ?意古人別自有術(shù)。

【今譯】

世上有能透光的鏡，鏡背面有銘文，共 20 字，字體非常古奧，沒有人能讀懂。用這面鏡子承受 日光，那么背面的花紋和 20 個字都透射到墻上，清清楚楚。有人探求它的道理，認(rèn)為是因為鑄造時薄 的地方先冷，唯獨有花紋和字的地方較厚，冷得慢，以致銅收縮要多一些。銘文和花紋雖然在背面， 但鏡面也會隱約可見。所以鏡子放在日光中就會現(xiàn)出來。我觀察這面鏡子，道理確實如此。但是我家 有三面鏡子，另外看見別人家收藏的鏡子，都是一樣的，圖案銘文沒有一點差異，樣式都非常古老。 只有那一面鏡子能透光，其它的鏡子也有非常薄的，卻都不能透光。由此想來，古人在造這面鏡子時自有別的方法。

【英譯】

Mengxi Bitan Chapter 19 Qiyong 12

I once saw a see-through mirror. ?Altogether twenty ancient Chinese characters were carved on its back, and ?they were undecipherable. If the mirror was put under the sunlight, the patterns and the characters would be clearly reflected on the wall. There were ? people who wanted to find out the reason for such a phenomenon. In their ?eyes, when the mirror was being cast its thinner parts cooled down first. As ?the parts carved with patterns and characters were thicker, they cooled down ?a bit more slowly, which caused the bronze to undergo deeper contraction. ?Though the patterns and characters were on the back of the mirror, their ?traces were still visible on the surface. That was why these patterns and characters were transparent in the sunlight. I once examined this mirror and ?thought that their explanation was reasonable. I have three mirrors in my own ?house, which, together with ancient mirrors that I find in other peoples’ ?houses, are of the same style, the same patterns and characters. However the ?sunlight can only make one of such mirrors transparent. Other mirrors are ?also thin, but the light cannot pass through them. I guess that the ancient ?artisans must have used a special method to make see-through mirrors.

Article by Tao Steven Zheng（鄭濤）?