"There will be new elements discovered, and they will fit into the empty spaces in my table."

"There exists everywhere a medium in things, determined by equilibrium."

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

"The periodic law is one of the most important generalizations in chemistry."

"The capital fact to note is that petroleum was born in the depths of the earth, and it is only there that we must seek its origin."