地球科学 1669

《天然封存于固体之中的固体——前驱》

尼古拉斯·斯泰诺（尼尔斯·斯滕森）

层层岩石是时间的书页——最底下那一层，最先写就。

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In depth · the introduction

一面有着条纹的岩壁，不只是风景。斯泰诺看出，它是一摞书页——而最底下那一页，最先写就。

把这个想法拆开看

斯泰诺注意到一件既简单又有力的事：泥、沙、石灰在水里以平整的层片沉降，一层压着上一层。所以在一堆未受扰动的岩石里，最底下的一层最老，最上面的一层最新。从底往上读一面岩壁，你读的就是顺着流的时间。

由此他引出了几条规则。岩层最初是平的，所以一层若是倾斜或褶皱的，那是后来被掀弯的。任何切穿这些层的东西——比方说一道灌进岩浆的裂缝——必定比它所切穿的层年轻。而封在岩石里的化石，先是活物，在岩石于它周围变硬之前就被埋了进去。这些规则合起来，就能让你一步步重建出一段无人亲见、却造就了一片地貌的事件先后。

解剖学家与那条鲨鱼

尼尔斯·斯滕森——拉丁化为尼古拉斯·斯泰诺——是一位才华横溢的年轻丹麦解剖学家，供职于佛罗伦萨那座光彩夺目的美第奇宫廷。1666 年，渔民在里窝那附近捕获一条巨鲨，大公命人把鲨头送到斯泰诺处解剖。它的牙齿，和人们几百年来从马耳他、托斯卡纳的岩石里挖出、称作「舌石」的东西一模一样——那些石头一直被当成自然的把戏，或是石化的蛇舌。斯泰诺看出了那个显而易见的答案：这些石头就是鲨鱼牙，被埋进后来变成岩石的泥里。这一个洞见，撬开了一个大得多的问题——固体之物如何会嵌进别的固体之中，又是谁先谁后？——读岩石的规则，正是由此而来。然后，出人意料地，斯泰诺转身离去：他皈依、当上神父、后来成为主教，散尽家财，再没有写出《前驱》所许诺的那部大书。

它为何重要

在斯泰诺之前，岩石是一本合着的书，化石不过是稀奇玩意。在他之后，地球有了一段你真能读出来的历史——一串记录在石头里的事件，最老的在最底。这就是地质学一切赖以站立的根基：相对定年、地质图、整张地质年代表。他读岩层的法子如此基本，以致今天显得理所当然——而这恰恰是一个伟大想法最可靠的标志。这套法子至今原样用着：考古学家用它为发掘定年，科学家用它为火星地表定序。

一摞旧报纸

想象门口那摞旧报纸，一个月来一份份摞了上去。就算没有日期，你也知道先后：最底下那份最先落下，最上面那份最后。要是一摊咖啡渍从最上面十份渗了下去、却没渗到第十一份，那这摊洒下来是在那十份已经摞好之后。斯泰诺读一面岩壁，分毫不差就是这样——岩层就是那些报纸，岩浆裂缝或侵蚀缺口就是那摊咖啡渍。

之前与之后

此前也有人猜过化石曾是活物——达·芬奇便是其中之一——但率先把规则刊印出来、并加以论证的，是斯泰诺。一个世纪后，詹姆斯·赫顿（hutton-1788）与查尔斯·莱尔（lyell-1830）用这些规则，论证出一个老得几乎无法想象的地球——「深时」；而莱尔的书被年轻的达尔文带上小猎犬号，给了演化所需要的那段浩瀚时间（darwin-1859）。以「年」计的真实年龄，要到二十世纪、靠放射性才有（patterson-1956）。此后的每一章——魏格纳（wegener-1912）与赫斯（hess-1962）那移动的大陆——都是在斯泰诺最先写下文法的那些岩层里读出来的。

The original document

Original source text

Nicolaus Steno (Niels Stensen, 1638–1686) · De solido intra solidum naturaliter contento dissertationis prodromus · Florence, 1669 · English: trans. J. G. Winter, Macmillan, 1916

A forerunner, never followed

The title says prodromus — a forerunner. Steno meant this short book as a preliminary sketch of a great dissertation on solids, which he never wrote: within a few years he left science for the priesthood. The forerunner alone turned out to contain the foundations of a science.

From a shark's head to the rocks

(Paraphrase.) Steno was a celebrated anatomist at the Medici court in Florence. In 1666 he dissected the head of a huge shark hauled ashore near Livorno and saw that its teeth were identical to the “tongue-stones” (glossopetrae) found embedded in the rocks of Malta and Tuscany. He concluded the tongue-stones were real shark teeth, buried in soft sediment that later hardened to stone. That forced the general problem of the book: when one solid body is found enclosed within another, how can we tell which formed first?

How to tell which solid formed first

(Paraphrase.) Steno's answer is read from the touching surfaces. If a body bears the impression of the one around it — a shell, a tooth, a crystal moulded against rock — then the moulding body already existed and is the older. Applied to rock layers, this becomes a rule for time.

The strata are a record of time

(Paraphrase.) Sediment settles out of a fluid in flat sheets, one upon another. So in any undisturbed pile, each layer is younger than the one beneath it — superposition — and the bottom layer is the oldest. Steno states it plainly:

At the time when any given stratum was being formed, all the matter resting upon it was fluid, and, therefore, at the time when the lowest stratum was being formed, none of the upper strata existed.

Original horizontality, lateral continuity — and a history

(Paraphrase.) Because sediment is laid down level and spreads until it thins or meets an obstacle, strata found tilted, broken, or ending at a cliff must have been disturbed after they formed — by collapse, uplift, or the carving of valleys. From such relations Steno argued that the rocks of Tuscany recorded a definite sequence of events, the first clear claim that the strata of the Earth hold a readable chronological history.

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Florence · 1669