I have a 1940 copy of "The Boy Electrician" given to me as a boy by the librarians when our small-town library closed. It includes a section on X-rays ("[X-ray

I have a 1940 copy of "The Boy Electrician" given to me as a boy by the librarians when our small-town library closed. It includes a section on X-rays ("[X-ray tubes] usually cost about four dollars and a half.") and shows how to connect the tube to a spark coil, how to make a fluoroscope and how to make photographs with X-rays. No warnings are present! This is a wonderful book because it covers so much ground and the writing and drawings give a physical sense of the topics: static electricity, magnetism, electrochemical cells, induction and capacitance, even semiconductors (cat's whisker detectors and selenium photocells).