Discontent is the first necessity of progress.

Invention is 1% inspiration and 99% perspiration

Time is really the only capital that any human being has, and the only thing he can't afford to lose.

Opportunity is missed by most people because it is dressed in overalls and looks like work.

The first requisite of success is the ability to apply your physical and mental energies to one problem without growing weary.

X-rays ... I am afraid of them. I stopped experimenting with them two years ago, when I came near to losing my eyesight and Dally, my assistant practically lost the use of both of his arms.

The trouble with most people is that they quit before they start.