26 



SCIENCE 



[N. S. Vol. XXVIII. No. 705 



" honey ants," is especially attractive because 

 of the accounts of the habits of all the known 

 honey ants of the world. These honey ants 

 have one form in which the abdomen is 

 swollen by stored honey. Such forms occur in 

 six widely separated genera. Our Myrme- 

 cocysius belong to two species, each with 

 several subspecies and varieties ; they inhabit 

 the arid regions of Mexico and the south- 

 western United States. The other paper is an 

 annotated list of the ants of Texas, New 

 Mexico, and Arizona." More ants occur in 

 this region than in all the rest of the United 

 States ; 101 species being recorded in this first 

 paper, 41 of which are in the genus Pheidole. 

 There are many notes on the habits of the 

 various species, and descriptions of several 

 new forms. 



Col. T. L. Casey has again published on 

 the darkling beetles." This time on the 

 Coniontinag, a group of moderate-sized in- 

 sects found in the western states. About two 

 hundred species are treated in synoptic form, 

 more than half are described as new, and 

 almost all are recorded from but one locality. 

 Several new genera are based on species 

 closely allied to Eusatius and (Joniontis. 



Making its initial appearance in the familiar 

 garb of the French society comes the Bulletin 

 de la Societe Entomologique d'Egypte. It is 

 published at Cairo in French, and under 

 French auspices. Fascicle 1 has forty pages, 

 and among other articles is one on the beetles 

 found in the Egyptian mummies. 



Nathan Banks 



SPECIAL ARTICLES 



REGIONS OP MAXIMUM IONIZATION DUE TO 

 GAMMA RADIATION 



1. I have recently standardized the fog 

 chamber by the aid of Thomson's electron. 

 The method (as will be shown elsewhere) is 



10 (( rjTjjg j^ig of Texas, New Mexico and Ari- 

 zona," Bull. Amer. Mus. Nat. Hist., XXIV., pp. 

 399-485, 1908, 2 pis., Part I. 



" " A Revision of the Tenebrionid Subfamily 

 Coniontinae," Proo. Wash. Acad. Sci., X., pp. 51- 

 166, 1908. 



not only expeditious, but leads by inversion, 

 when my old values of the nucleations of the 

 coronas are inserted, to values of e which 

 agree with Thomson's and other estimates. 

 This affords an incidental check on the 

 broader bearings of the work. Thus a series 

 of rough tests made in this way showed 

 e X 10^° to lie between 3 and 4 els. units, 

 agreeing closely enoiigh with the accepted 

 values to prove that both the positive and the 

 negative ions are captured in my fog cham- 

 bers, even at very high nucleations (500,000 

 per cu. cm.). 



2. The experiments themselves run smoothly 

 and take but a few minutes each; but there is 

 an inherent difficulty involved in the inter- 

 pretation of the distributions of ionization ob- 

 served in the fog chamber. The radium (10 

 mg., 100,000, contained in a small thin sealed 

 glass tube) is introduced into the inside of a 

 cylindrical fog chamber, by aid of an alumi- 

 num tube (walls 1 mm. thick and about one 

 quarter of an inch in diameter), thrust axially 

 from one end to the other of the horizontal 

 chamber. The inner end of the aluminum 

 tube is thoroughly sealed; the other end lies 

 quite outside the fog chamber, is open, and 

 serves for the introduction of the radium tube. 

 In this way the latter may be moved axially 

 from the glass end of the fog chamber on the 

 right of the observer, to the metal cap which 

 closes the fog chamber on the left. 



When the radium is successively placed at 

 distances of about 11 cm. apart within the 

 available 45 cm. the length of the fog cham- 

 ber, the maximum nucleation (ionization) 

 coincides with the position of the radium 

 when both are near the glass end of the 

 chamber (12 cm. in diameter). The nuclea- 

 tion then falls off rapidly and at first uni- 

 formly from the glass end to the metal end, 

 where the coronas are strikingly smaller and 

 the nucleation less than one half of that ob- 

 served at the glass end. Considered alone, 

 this would appear like the natural effect of an 

 increasing distance from the source, except 

 that the coronas near the distant end approach 

 a constant diameter. 



When the radium is moved about 12 cm. 



