I have achieved an inner freedom.

The elements, if arranged according to their atomic weights, exhibit an apparent periodicity of properties.

When the elements are arranged in vertical columns according to increasing atomic weight, so that the horizontal lines contain analogous elements again according to increasing atomic weight, an arrangement results from which several general conclusions may be drawn.

There is nothing in this world that I fear to say.

Work, look for peace and calm in work: You will find it nowhere else. Pleasures flit by -- they are only for yourself; work leaves a mark of long-lasting joy, work is for others.

No law of nature, however general, has been established all at once; its recognition has always been preceded by many presentiments.

The edifice of science not only requires material, but also a plan. Without the material, the plan alone is but a castle in the air-a mere possibility; whilst the material without a plan is but useless matter.