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.
Dmitri MendeleevThe 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.
Dmitri MendeleevNo law of nature, however general, has been established all at once; its recognition has always been preceded by many presentiments.
Dmitri Mendeleev