Chemists cannot actually weigh the mass of an atom of an element on a pair of scales, or by any other method. But if we put down 16 as the “atomic weight” of oxygen, and ascertain the “combining weight” (ratio) of hydrogen to oxygen, we can determine the “atomic weight” of hydrogen (1.008). (See Shipley, “The A B C of the Electron Theory of Matter,” p. 14, Little Blue Book, No. 603.) The ratio of the masses of _any_ two elements in a chemical compound can be very accurately determined. Without going into the details here, it may be said that the _relative_ weights of the atoms of any element can be determined to 0.01% in many cases (by chemical analysis and synthesis); while the _actual_ weight of any atom has not yet been determined to better than 0.1%. HOW RADIUM IS CONVERTED TO LEAD Lead is produced from uranium by a successive series of losses of Alpha particles--or helium atoms. Omitting the less essential outcomes, or transition stages, we find that each atom of uranium spontaneously ejects three atoms of another element, helium, and thereby is converted into still another element, radium. By losing one atom of helium, radium, in turn, is converted into the so-called emanation, or _niton_. The latter quickly loses four more atoms of helium and is converted into lead, “uranium lead,” having an atomic weight of 206.08. Ordinary (common) lead, constituting the vast bulk of the lead of the world, has a much higher atomic weight, namely, 207 (Prof. Theodore Richards). Lead from thorium has an atomic weight of 208; from actinium, 206. So we have, in fact, four kinds of lead. Omitting the less stable transition products, we may say, then, that an atom of uranium is converted into lead by the loss of eight atoms of helium--losing three to become radium, then one to become the emanation, and finally four to become lead. No known human agency can either retard or hasten this breaking down of the uranium atom into radium, or of the radium into emanation, with the final production of lead. This statement has been universally accepted as true. Nevertheless, Dr. A. Glaschler stated (_Nature_ [London], September 12, 1925) that he had succeeded in accelerating the change of uranium to uranium X (the first product of uranium 1) by submitting uranium oxide to “strong rushes of momentary high-tension currents.” As early as 1923, A. Nodon (_Comp. rend., 176_, 1705 [1923]) brought forward strong evidence of an increase of the activity of radioactive substances when outdoors and enclosed by envelopes of small absorbing power for Gamma rays as contrasted to the smaller radioactivity of the same substances in cellars and when heavily enveloped by lead. For a tentative explanation of this phenomenon, see _Science_, January 8, 1926 (Vol. LXIII, No. 1619), pp. 44–45. Both uranium and thorium, as we have just stated, break down and become radium, then change to helium and lead.