Nothing is so ignorant as a man's left hand, except a lady's watch.

In the laboratory there are no fustian ranks, no brummagem aristocracies; the domain of Science is a republic, and all its citizens are brothers and equals, its princes of Monaco and its stonemasons of Cromarty meeting, barren of man-made gauds and meretricious decorations, upon the one majestic level!

We need not worry so much about what man descends from; it's what he descends to that shames the human race.

...mastery of the art and spirit of the Germanic language enables a man to travel all day in one sentence without changing cars.

I notice that you use plain, simple language, short words and brief sentences. That is the way to write English―it is the modern way and the best way. Stick to it; don't let fluff and flowers and verbosity creep in. When you catch an adjective, kill it. No, I don't mean utterly, but kill most of them―then the rest will be valuable. They weaken when they are close together. They give strength when they are wide apart. An adjective habit, or a wordy, diffuse, flowery habit, once fastened upon a person, is as hard to get rid of as any other vice.

I make it a rule never to smoke while I'm sleeping.

I do not see how astronomers can help feeling exquisitely insignificant, for every new page of the Book of the Heavens they open reveals to them more and more that the world we are so proud of is to the universe of careening globes as is one mosquito to the winged and hoofed flocks and herds that darken the air and populate the plains and forests of all the earth. If you killed the mosquito would it be missed? Verily, What is Man, that he should be considered of God?