I had only ordinary capacity but extraordinary persistency.

The love of one's own sex is precious, for it is neither provoked by vanity nor retained by flattery; it is genuine and sincere.

But why look back at all? Why turn your eyes to your shadow, when, by looking upward, you see your rainbow in the same direction?

How strange that some people cannot believe in both the Book of Nature and the Book of God.

Besides learning to see, there is another art to be learned - not to see what is not.

Every formula which expresses a law of nature is a hymn of praise to God.

I made observations for three hours last night, and am almost ill today from fatigue; still I have worked all day, trying to reduce the places, and mean to work hard again tonight.