I have discovered that a screw-shaped device such as this, if it is well made from starched linen, will rise in the air if turned quickly.

Just as iron rusts from disuse... even so does inaction spoil the intellect.

Every now and then go away, have a little relaxation, for when you come back to your work your judgment will be surer.

No human investigation can be called real science if it cannot be demonstrated mathematically.

A bird is an instrument working according to mathematical law, which instrument it is within the capacity of man to reproduce with all its movements, but not with a corresponding degree of strength, though it is deficient only in the power of maintaining equilibrium. We may therefore say that such an instrument constructed by man is lacking in nothing except the life of the bird, and this life must needs be supplied from that of man.

Learning is the only thing the mind never exhausts, never fears, and never regrets.

The cat is nature's masterpiece.