276 



SCIENCE 



[N. S. Vol. XXXVIII. No. 973 



atom must be two, or haK its atomic weight — 

 also in agreement with the Eutherford theory. 

 So far so good. But when we consider the 

 hydrogen and helium spectra, we get into 

 difficulty immediately. Stark, Fischer and 

 Kirschbaum," from a recent careful study of 

 the Stark-Doppler eilect in connection with 

 helium canal rays, conclude that the series of 

 single lines which Eunge and Paschen ascribe 

 to " parhelium " are emitted by the doubly 

 charged helium atom. Also, according to 

 Stark's hypothesis (which, though not proved, 

 yet seems probable from certain indirect evi- 

 dence) the hydrogen series lines are emitted 

 by the single charged hydrogen atom. Now, 

 both the " parhelium " and the hydrogen series 

 lines show the normal Zeeman effect and there- 

 fore can not be emitted by systems devoid of 

 vibrating electrons. Stark's hypothesis there- 

 fore demands a more complex atom; it is in- 

 compatible with the Eutherford theory as far 

 as hydrogen and helium are concerned. 



Also, recent experiments seem to associate 

 the compound spectrum of hydrogen with the 

 positively charged molecule. It is of course 

 enormously complex. Many of its lines show 

 a normal Zeeman effect, others an abnormal 

 effect, others apparently no effect at all.' How 

 such a spectrum can be due to the vibrations 

 of a single electron around two positive nu- 

 clei seems inconceivable. 



Certainly the Eutherford atom seems much 

 too simple to explain these spectral phenomena, 

 though perhaps these and other objections may 

 be overcome. Is this conception of the atom 

 the only one which leads to the expression for 

 the distribution of scattered a rays which 

 Geiger and Marsden have so thoroughly veri- 

 fied? If possible, the scattering effect of 

 hydrogei should be tested. Perhaps this might 

 be done by the use of a compound of hydrogen 

 or liquid hydrogen. Such experiments on the 

 scattering of a and fi rays seem our most 

 promising means of securing more exact knowl- 

 edge of the actual structure of atoms; but the 

 conceptions thus suggested must explain or be 

 in accord with a wide variety of atomic phe- 

 'Ann. d. Phys., 40: 499, March, 1913. 

 'Dufour, Annal. cMm. phys. (8), 9: 413, 1906. 



nomena before they can expect general accept- 

 ance. Gordon S. Fuloher 

 Univeesitt op Wisconsin, 

 June 27, 1913 



NOTES ON ENTOMOLOGY 

 Economic entomologists will welcome the 

 appearance of a new monthly journal — The 

 Review of Applied Entomology. It is pub- 

 lished in London (Dulau & Co.) and issued 

 in two series: series A, agricultural; series B, 

 medical and veterinary. It consists almost 

 wholly of reviews of other works, or reports 

 sent in by various investigators. The journal 

 is supported by the Imperial Bureau of Ento- 

 mology, and Guy A. K. Marshall is the editor, 

 while a series of distinguished entomologists 

 and naturalists form a committee of manage- 

 ment. The parts so far issued average 32 

 pages for series A, and 20 pages for series B. 

 In series B there are references to new species 

 in certain groups of general medical impor- 

 tance, as mosquitoes and Tabanidse. 



The perfection of preservation of the amber 

 insects has made them a most attractive field 

 of study. Most fossil insects are so discour- 

 agingly imperfect, that a knowledge of the 

 actual structural details of some prehistoric 

 insects is a most welcome contribution to the 

 phylogeny of the group. And when this is 

 brought out by so able a specialist in the 

 group as by Dr. G. Ulmer in his " Amber 

 Trichoptera " ' we can place confidence in the 

 interpretations. Probably the most important 

 point is that the Limnephilidse, now a domi- 

 nant family in northern Europe, is lacking in 

 amber, although all other families are repre- 

 sented, and the Sericostomatidse by many re- 

 markable genera. The presence of a few 

 genera such as Ganonema, Marilia and Tri- 

 plectides, now occurring in tropical regions, 

 give one the impression (probably erroneous) 

 of a warmer climate. Besides describing in 

 detail the genera (66) and species (152) 

 known from amber Dr. Ulmer presents many 

 • ' ' Die Trichopteren des Baltischen Bernsteins, ' ' 

 Sehriften Physik.-Okonom. Gesellseh. Konigsberg; 

 Beitrage zur Naturkunde Preussens, Heft 10; 380 

 pages, 480 figs., 1912. 



