= Röntgen X-ray discovery experiment
{c}
<Wilhelm Conrad Röntgen>'s 1895 first communication describes an <induction coil> driving an evacuated <gas-discharge tube>, enclosed in black cardboard in darkness. A paper screen coated with <barium platinocyanide> showed <fluorescence> even with its uncoated side facing the tube, visible two metres away. The covering excluded ordinary illumination.<On a New Kind of Rays by Wilhelm Conrad Röntgen>[Röntgen, On a New Kind of Rays, §§1–2; inspected reprint p. 153]{ref}
He interposed materials: a thousand-page book transmitted; $1.5\,\mathrm{mm}$ lead was practically opaque. A stepped stack of foil produced a <photographic plate> record. Different materials were not equivalent at equal density and thickness. <Photographic plates> checked visual observations while remaining covered against ordinary illumination.<On a New Kind of Rays by Wilhelm Conrad Röntgen>[First communication, §§2–6; reprint pp. 153–154: absorption tests and photographic controls]{ref}
Section 14 lists photographs of hand bones, wire on a bobbin, boxed weights, an enclosed compass, and a lead-painted door. It does not identify the hand's owner. Magnetic deflection moved the <cathode ray> impact point and thus the source, without bending the emerging <X-rays>. Their nature remained unsettled.<On a New Kind of Rays by Wilhelm Conrad Röntgen>[First communication, §§11–14 and 17; reprint pp. 156–157]{ref}
The observations belong to 1895; the contemporary English translation appeared in Nature on 23 January 1896.<On a New Kind of Rays by Wilhelm Conrad Röntgen>[Catalogue, On a new kind of rays: notes identify the Nature translation and its publication date]{ref} The experimental logic separates production, transmission and detection. A visibly opaque covering can transmit <X-rays>; <fluorescence> then converts deposited <energy> into visible <light>. A shadow measures a difference between paths through an object, rather than a direct view of its surface. Neither a screen's brightness nor photographic darkness alone measures an absolute <X-ray> <energy> or establishes the <X-ray attenuation> law below.
Back to article page
