Source

Thomas Henry Huxley, On a Piece of Chalk, Discourses: Biological and Geological Essays, public domain.

Passage

A great chapter of the history of the world is written in the chalk. Few passages in the history of man can be supported by such an overwhelming mass of direct and indirect evidence as that which testifies to the truth of the fragment of the history of the globe, which I hope to enable you to read, with your own eyes, to-night. Let me add, that few chapters of human history have a more profound significance for ourselves. I weigh my words well when I assert, that the man who should know the true history of the bit of chalk which every carpenter carries about in his breeches-pocket, though ignorant of all other history, is likely, if he will think his knowledge out to its ultimate results, to have a truer, and therefore a better, conception of this wonderful universe, and of man’s relation to it, than the most learned student who is deep-read in the records of humanity and ignorant of those of Nature.

The language of the chalk is not hard to learn, not nearly so hard as Latin, if you only want to get at the broad features of the story it has to tell; and I propose that we now set to work to spell that story out together.

We all know that if we “burn” chalk the result is quicklime. Chalk, in fact, is a compound of carbonic acid gas, and lime, and when you make it very hot the carbonic acid flies away and the lime is left. By this method of procedure we see the lime, but we do not see the carbonic acid. If, on the other hand, you were to powder a little chalk and drop it into a good deal of strong vinegar, there would be a great bubbling and fizzing, and, finally, a clear liquid, in which no sign of chalk would appear. Here you see the carbonic acid in the bubbles; the lime, dissolved in the vinegar, vanishes from sight. There are a great many other ways of showing that chalk is essentially nothing but carbonic acid and quicklime. Chemists enunciate the result of all the experiments which prove this, by stating that chalk is almost wholly composed of “carbonate of lime.”

Vocabulary

Word / Phrase Meaning TOEFL Note
overwhelming mass a very large and persuasive amount Often describes evidence or data.
testifies to gives evidence for Academic synonym for shows or supports.
profound significance deep importance Common in humanities and science passages.
conception a formed understanding or idea Often means a theory-like view.
enunciate state clearly and formally A high-value academic verb.

Sentence Work

Few passages in the history of man can be supported by such an overwhelming mass of direct and indirect evidence as that which testifies to the truth of the fragment of the history of the globe.

先抓主干，再处理插入语和修饰成分。TOEFL 阅读里，这类句子常考作者如何限定前一句的解释力。

Structure Notes

surprising claim -> larger significance -> accessible metaphor -> concrete experiment

Writing Takeaway

Begin with a surprising claim, connect it to a larger question, reassure the reader, and then give a concrete demonstration.