“In a few minutes there was no doubt about it. Rays were coming from the tube which had a luminescent effect upon the paper.”
The New Marvel in Photography (1896)
Context: I was working with a Crookes tube covered by a shield of black cardboard. A piece of barium platino-cyanide paper lay on the bench there. I had been passing a current through the tube, and I noticed a peculiar black line across the paper. … The effect was one which could only be produced, in ordinary parlance, by the passage of light. No light could come from the tube, because the shield which covered it was impervious to any light known, even that of the electric arc. … I did not think; I investigated. I assumed that the effect must have come from the tube, since its character indicated that it could come from nowhere else. I tested it. In a few minutes there was no doubt about it. Rays were coming from the tube which had a luminescent effect upon the paper. I tried it successfully at greater and greater distances, even at two metres. It seemed at first a new kind of invisible light. It was clearly something new, something unrecorded.
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Wilhelm Röntgen 6
German physicist 1845–1923Related quotes

"A New Method of Obtaining Very Great Moving Powers at Small Cost" (1690)

Quoted in 'Tesla, 75, Predicts New Power Source', New York Times (5 Jul 1931), Section 2, 1.

Variant: The key to wisdom is this - constant and frequent questioning, for by doubting we are led to question and by questioning we arrive at the truth.

Source: Cibola Burn (2014), Chapter 47 (p. 481)

The Spirit of Revolt (1880)
Context: The direction which the revolution will take depends, no doubt, upon the sum total of the various circumstances that determine the coming of the cataclysm. But it can be predicted in advance, according to the vigor of revolutionary action displayed in the preparatory period by the different progressive parties. … The party which has made most revolutionary propaganda and which has shown most spirit and daring will be listened to on the day when it is necessary to act, to march in front in order to realize the revolution.

“… nature often produces combinations and effects which on paper appear incorrect.”
Source: Practical Pictorial Photography, 1898, Illumination of clouds and the direction of light, p. 101

John Banville on the birth of his dark twin, Benjamin Black (2011)