X
X-rays. A curious phenomenon involving the radiation of invisible rays of light, which have the power to travel through various opaque bodies. The rays are used in detecting foreign substances in the human body and for photographing invisible or hidden objects without disturbing their surroundings.
X-ray Lamp. A high vacuum tube lamp whose interior walls are covered with crystals of calcium or other fluorescent substances, and which, when exposed to the X-rays, give out a luminous light.