A man who has taken your time recognises no debt; yet it is the one he can never repay.

Many discoveries are reserved for ages still to come . . . . Our universe is a sorry little affair unless it has in it something for every age to investigate.

I require myself not to be equal to the best, but to be better then the bad.

Death falls heavily on that man who, known too well to others, dies in ignorance of himself.

What nature requires is obtainable, and within easy reach. It is for the superfluous we sweat.

Those that are a friend to themselves are sure to be a friend to all.

The great blessings of mankind are within us and within our reach; but we shut our eyes, and, like people in the dark, we fall foul upon the very thing we search for, without finding it.