Page:Harper's New Monthly Magazine - v109.djvu/99



ORTUNATELY it is possible for every one with a guinea to spare to become the possessor of a tiny speck of the most expensive and rare and wonderful of all known substances. And it is convenient for the writer upon radium that Sir William Crookes has invented the spinthariscope, a little scientific toy which needs no skill to use, and demonstrates very perfectly the most astounding of all the astounding properties of radium. I must make a start with the spinthariscope, which most of my readers have doubtless seen, and will help thereby myself in treating of a very complex subject.

The spinthariscope is a little tube, about an inch and a half long, closed at one end, and having a couple of magnifying lenses at the other. On the inner surface of the blind end is a little bit of paper covered with tiny yellow crystals of a salt called zinc sulphide. A little metal pointer, like the hand of a watch, stands out in front of this piece of paper, and on the end of the pointer is a speck of radium—much too small to be seen by the naked eye. Go into a dark room with the spinthariscope and hold it as close as possible to one eye. At once you see a shower of points of light, that come from the surface of the zinc-sulphide paper. That shower of sparks never ceases, night or day, year in, year out. The invisible morsel of radium will keep the spinthariscope going like that for at least thirty thousand years—a period five times as long as that of recorded history. In time you may have to renew the bit of paper, for M. Becquerel has shown that the flashes of light are probably due to the splintering of the little crystals by something that flies out from the radium; and after that has been going on incessantly for a few years there can hardly be any crystals left. One point worth noting is that, for some reason or other entirely unconnected with the radium, the spinthariscope works better when it is not too cold. We know that the radium has nothing to do with this fact, for radium works just as well in liquid air or hydrogen, at a temperature more than two hundred degrees below zero, as it does at ordinary temperatures. No power we know affects the properties of this extraordinary substance.

Now the sight which the spinthariscope affords is really the vindication of the much-abused alchemists who sought to turn the baser metals into gold. Later generations laughed at them and said: "Oh no; you cannot transmute one element into another, for each element has its own kind of atom; and the atoms are the unalterable foundation-stones of the universe. They cannot be changed one into another, and so you cannot change lead into gold. Your philosopher's stone is a myth." But this supposed impossible thing is precisely what is happening in the spinthariscope. Let us consider the facts.

Radium is certainly an "element"—as much an element as gold or lead or any other. Now the atoms of any element have a characteristic weight of their own. If we represent the weight of a hydrogen atom—the lightest of all—by the figure 1, then the radium atom, according to Madame Curie, its discoverer, is 225. It is very heavy indeed. Only two heavier substances are known, thorium (232) and uranium (240); and these two share the remarkable properties of radium. Now if you confine some of this "element" in a tube and wait a little, there appears in the tube after a time a minute quantity of a gas which was not there before. It is not gaseous radium, for when it is examined with the spectroscope it shows a spectrum quite different from that of radium; in fact, its spectrum is quite different from that of any known substance. But it was discovered by Sir William Ramsay that if the spectrum of