816 CURRENT TOPICS. [J. F. I.

The Nuclei of Atoms and the New Periodic System. W . D . HARKINS. (Physical Review, February, i92o . ) - -Formul~e are g iven for the composi t ion of the a toms and of the nuclei of the first 27 elements and of the radio-active elements. An atom of sul- phur is g iven as cons is t ing of 8 helium atoms, while its nucleus is made up of the s ame n u m b e r of hel ium nuclei. No th ing but hel ium and hydrogen a toms appear in the formulae for atoms, but in the nuclei there are also beta part icles in addit ion to the nuclei of the two e lements jus t ment ioned. In general the nuclei of the even numbered light elements consist altogether of helium nuclei, while the odd numbered e lements have in their nuclei an addi- t ional group, consis t ing of 3 hydrogen nuclei and 2 beta particles. The elements f rom 28 to 80 in atomic number do not fall in with this scheme, and it is suggested that they may consist of mixtures of isotopes.

" In a note appended at the t ime of correc t ing the proof for this paper, the wr i te r s ta tes tha t his latest a tomic weigh t resul ts seem to indicate tha t he has obta ined an exper imenta l separa t ion of chlorine into isotopes ."

G. F. S.

Nature of the Process of Ionization of Gases by AllSha Rays. R. A. MILLIKAN, V. H. GOTTSCIIALK and M. J. KELLY. (Phys. Rev., March, I92O , p. I 57. ) - - A l p h a rays f rom radium bombar@e'd the mole- cules of air, carbon dioxide, carbon tetrachloride, methyl iodide and mercury dimethyl. Thus atoms of H, C, O, N, C1, I and Hg, with a range of atomic weight f rom I to 200, were traversed by the rapidly moving rays. The residues of t h e ionized atoms were caught on oil drops and their electrical charges measured. This was done in 290o cases of which only five corresponded to double charges and none at all to triple or larger charges. " The results prove that, at least, 99 times out of IOO, ionizatio.rt by an Alpha ray, in the case of each of the gases and vapors studied, consists in the detachment of a single eletron f rom a molecule."

G. F. S.

Digestibility of Chicken Skin.~FDwARD F. KOItMAN and H. A. SHONLE (Journal of Biological Chemistry, I92O, xli, 469-472) have made me tabo l i sm exper imen t s on human subjects concern ing the ut i l izat ion of the prote ins or n i t rogenous cons t i tuents and the fat of the skin of the c o m m o n fowl. The resul ts showed that , when 65.I to 67. 5 per cent. of the nitrogen of the diet was supplied by chicken skin, the ut i l izat ion of the n i t rogen was as good as when the same propor t ion of the n i t rogen was supplied by meat , eggs, and milk. T h e ut i l izat ion of the ingested fat l ikewise was prac- t ical ly the same on the chicken-skin diet, and on the diet of meat , eggs, and milk.

J. s. n .