[T]he rare earth elements perplex us in our researches, baffle us in our speculations, and haunt us in our very dreams. They stretch like an unknown sea before us mocking, mystifying and murmuring strange revelations and possibilities.
As quoted in Nature's Building Blocks: An A-Z Guide to the Elements (New Edition) by John Emsley (page 266)
Most students of nature sooner or later pass through a process of writing off a large percentage of their supposed capital of knowledge as a merely illusory asset. As we trace more accurately certain familiar sequences of phenomena we begin to realize how closely these sequences, or laws , as we call them, are hemmed round by still other laws of which we can form no notion. With myself this writing off of illusory assets has gone rather far and the cobweb of supposed knowledge has been pinched (as some one has phrased) into a particularly small pill.William Crookes
Which was first, Matter or Force? If we think on this question, we shall find that we are unable to conceive of matter without force, or force without matter. When God created the elements of which the earth is composed, He created certain wondrous forces, which are set free and become evident when matter acts on matter.William Crookes
Our alleged facts might be true in all kinds of ways without contradicting any truth already known. I will dwell now on only one possible line of explanation, not that I see any way of elucidating all the new phenomena I regard as genuine, but because it seems probable I may shed a light on some of those phenomena. All the phenomena of the universe are presumably in some way continuous; and certain facts, plucked as it were from the very heart of nature , are likely to be of use in our gradual discovery of facts which lie deeper still.William Crookes