Nothing more passed between us during the journey back, and we hurried directly to the laboratory, late as it was. Kennedy had evidently been revolving something over and over in his mind, for the moment he had switched on the light, he unlocked one of his air-and dust-proof cabinets and took from it an instrument which he placed on a table before him.
It was a peculiar-looking instrument, like a round glass electric battery with a cylinder atop, smaller and sticking up like a safety valve. On that were an arm, a dial, and a lens fixed in such a way as to read the dial. I could not see what else the rather complicated little apparatus consisted of, but inside, when Kennedy brought near it the pole of a static electric machine two delicate thin leaves of gold seemed to fly wide apart when it was charged.
Kennedy had brought the glass tray near the thing. Instantly the leaves collapsed and he made a reading through the lens.
“What is it?” I asked.
“A radioscope,” he replied, still observing the scale. “Really a very sensitive gold leaf electroscope, devised by one of the students of Madame Curie. This method of detection is far more sensitive even than the spectroscope.”
“What does it mean when the leaves collapse?” I asked.
“Radium has been near that tray,” he answered. “It is radioactive. I suspected it first when I saw that violet color. That is what radium does to that kind of glass. You see, if radium exists in a gram of inactive matter only to the extent of one in ten-thousand million parts its presence can be readily detected by this radioscope, and everything that has been rendered radioactive is the same. Ordinarily the air between the gold leaves is insulating. Bringing something radioactive near them renders the air a good conductor and the leaves fall under the radiation.”
“Wonderful!” I exclaimed, marveling at the delicacy of it.
“Take radium water,” he went on, “sufficiently impregnated with radium emanations to be luminous in the dark, like that water of Denison’s. It would do the same. In fact all mineral waters and the so-called curarive muds like fango are slightly radioactive. There seems to be a little radium everywhere on earth that experiments have been made, even in the interiors of buildings. It is ubiquitous. We are surrounded and permeated by radiations—that soil out there on the campus, the air of this room, all. But,” he added contemplatively, “there is something different about that tray. A lot of radium has been near that, and recently.”
“How about that bandage about Haughton’s neck?” I asked suddenly. “Do you think radium could have had anything to do with that?” “Well, as to burns, there is no particular immediate effect usually, and sometimes even up to two weeks or more, unless the exposure has been long and to a considerable quantity. Of course radium keeps itself three or four degrees warmer than other things about it constantly. But that isn’t what does the harm. It is continually emitting little corpuscles, which I’ll explain some other time, traveling all the way from twenty to one hundred and thirty thousand miles a second, and these corpuscles blister and corrode the flesh like quick-moving missiles bombarding it. The gravity of such lesions increases with the purity of the radium. For instance I have known an exposure of half an hour to a comparatively small quantity through a tube, a box and the clothes to produce a blister fifteen days later. Curie said he wouldn’t trust himself in a room with a kilogram of it. It would destroy his eyesight, burn off his skin and kill him eventually. Why, even after a slight exposure your clothes are radioactive—the electroscope will show that.”