He switched on the electric current, and the apparatus began to sputter.  The pungent odor of ozone from the electric discharge filled the room.  Through the lead-glass bowl I could see the X-ray tube inside suffused with its Peculiar, yellowish-green light, divided into two hemispheres of different shades.  That, I knew, was the cathode ray, not the X-ray, for the X-ray itself, which streams outside the tube, is invisible to the human eye.  The doctor placed in our hands a couple of fluoroscopes, an apparatus by which X-rays can be detected.  It consists simply of a closed box with an opening to which the eyes are placed.  The opposite end of the box is a piece of board coated with a salt such as platino-barium cyanide.  When the X-ray strikes this salt it makes it glow, or fluoresce, and objects held between the X-ray tube and the fluoroscope cast shadows according to the density of the parts which the X-rays penetrate.

With the lead-glass bowl removed, the X-ray tube sent forth its wonderful invisible radiation and made the back of the fluoroscope glow with light.  I could see the bones of my fingers as I held them up between the X-ray tube and the fluoroscope.  But with the lead-glass bowl in position over the tube, the fluoroscope was simply a black box into which I looked and saw nothing.  So very little of the radiation escaped from the bowl that it was negligible—­except at one point where there was an opening in the bottom of the bowl to allow the rays to pass freely through exactly on the spot on the patient where they were to be used.

“The dermatitis, they say, has appeared all over her body, particularly on her head and shoulders,” added Dr. Gregory.  “Now I have shown you my apparatus to impress on you how really impossible it would have been for her to contract it from her treatments here.  I’ve made thousands of exposures with never an X-ray burn before—­except to myself.  As for myself, I’m as careful as I can be, but you can see I am under the rays very often, while the patient is only under them once in a while.”

To illustrate his care he pointed out to us a cabinet directly back of the operating-table, lined with thick sheets of lead.  From this cabinet he conducted most of his treatments as far as possible.  A little peep-hole enabled him to see the patient and the X-ray apparatus, while an arrangement of mirrors and a fluorescent screen enabled him to see exactly what the X-rays were disclosing, without his leaving the lead-lined cabinet.

“I can think of no more perfect protection for either patient or operator,” said Kennedy admiringly.  “By the way, did Mrs. Close come alone?”

“No, the first time Mr. Close came with her.  After that, she came with her Trench maid.”

The next day we paid a visit to Mrs. Close herself at the private hospital.  Kennedy had been casting about in his mind for an excuse to see her, and I had suggested that we go as reporters from the Star.  Fortunately after sending up my card on which I had written Craig’s name we were at length allowed to go up to her room.