SAT R&W W15: The Transition Traps — Two Choices That Mean the Same Thing

Tide mills were built where a creek could be dammed at high water and the stored water released through a wheel as the tide fell. They ran on a schedule set by the moon rather than by the working day, and a miller might be at the wheel at three in the morning. the mills were abandoned within a generation of the steam engine, which ran whenever it was fed.

Bamboo reaches its full height in a single season and can be cut every three years without replanting, which makes it attractive as a building material. the stems split along their length when they dry unevenly, and the joints that give timber its strength cannot be cut into a hollow tube.

A word processor's spell-checker catches misspellings but not the wrong word correctly spelled, and professional proofreaders still find several errors per thousand words in checked text. the errors it does catch are the ones a reader would have noticed anyway, while the ones it misses are precisely those a tired reader slides past.

Some materials fail without warning. Glass does not bend before it breaks, and a ceramic bearing that has run soundly for a decade can shatter in a single revolution. engineers who use such materials design to a far larger margin than the measured strength alone would suggest.