May 26, 1 9 10] 



NATURE 



369 



re-state my general formula, with interchanged letters, as 

 below : — 



The condition that each quarter shall be equal to 

 A+B+C+D is obviously a—c + d=o. Substituting 

 — a + c for d, the universal formula for a square in equal 

 quarters is therefore : — 



which, by putting A + a, B+b, C + c, for A, B, C, re- 

 spectively, becomes : — 



This is the familiar traditional form, being the addition 

 of one Latin square (A, B, C, D) to another (o, a, b, c). 

 It is usually written (inaccurately) as if it involved eight 

 arbitrary variables, instead of seven. 



Ernest Bergholt. 



Windsor House, Bream's Buildings, E.G. 



Magnetic Deflection of j3 Rays. 



The nature of the emission of a rays from radio-active 

 bodies, and the mechanism of their absorption when pass- 

 ing through matter, are well known from the experiments 

 of Rutherford, Bragg, and others. 

 . As regards /5 rays, our knowledge is not so complete. 

 Although in recent years a large number of experiments 

 have been undertaken in order to study the laws of their 

 absorption, there still remains considerable doubt concern- 

 ing several fundamental points. From the study of the 



NO. 21 17, VOL. 83] 



absorption of $ rays emitted from different radio-active 

 substances, Otto Hahn and Lise Meitner arrived at the 

 conclusion that the /8 rays, in the same way as a rays, are 

 characterised by a definite initial velocity of expulsion. 

 For different i3-ray products the velocity may, of course, 

 be different, but for a simple substance this velocity is 

 characteristic of the rays. It was assumed by Hahn and 

 Meitner that a homogeneous substance could be recognised 

 as such by the exponential law of absorption by aluminium 

 of the P ra\ s which are emitted. 



The experiments of W. Wilson were not in accord with 

 this hypothesis. He found that the exponential law is not 

 a measure of the homogeneity of the radiation, but, on 

 the contrary, that homogeneous rays are absorbed according 

 to a linear law. 



In addition, the experiments of Kaufmann and Bucherer, 

 who obtained a continuous magnetic spectrum of /3 rays 

 in their determination of efm and v for those rays, 

 appeared to be contrary to the view of Hahn and Meitner.- 

 Such a spectrum could not be obtained on the assumption 

 of groups of homogeneous /3 rays. 



During the last few months the authors have investigated 

 by a photographic method the magnetic deflection of 

 /8 rays, and were able to show that in some cases very 

 well-defined lines of deflection can be obtained. Experi- 

 ments were especially successful when the active deposit 

 from thorium ser\ed as source of radiation. As Hahn 

 and Meitner have shown, this contains two groups of rays 

 (ThA and ThD). The authors obtained in this case two 

 distinctly separated lines in the magnetic field. The Mne 

 due to thorium A, which was further deflected, was nearly 

 as well defined as if it were produced bv a rays. Of 

 course, by use of a stronger field, a third line, fairly well 

 marked, was absorbed verj- near the ThA line, the source of 

 which we are not yet quite certain. 



But it is of interest that Hahn and Meitner recently dis- 

 covered a new easily absorbed P radiation in ThX, and 

 that the photographic impression, when using thorium X, 

 really gave one more line as when using the active deposit 

 alone. 



Mesothorium gave a number of w^ell-separated lines 

 (about five or six). In this case the absorption experiments 

 of Hahn and Meitner had already indicated a complex 

 /3 radiation. 



In the case of radium we have not, so far, been able to 

 obtain single bands. This may perhaps be ascribed to the 

 fact that the /8 rays from the radium products do not differ 

 much in their velocities, and that the bands were con- 

 sequently superposed, the intensity of the magnetic field 

 being only about 80 Gauss. As a whole, the photographic 

 impressions produced by the hard /5 rays are not very 

 clear, since the rays pass through the photographic film 

 without appreciable absorption, giving rise to a secondary 

 radiation which fogs the plate. 



The authors have proved by their experiments, at least 

 for several of the radio-active elements, that these elements 

 emit groups of /3 rays of definite velocity for which e/tn 

 and V can be separately determined. 



A more detailed account of these experiments will be 

 published elsewhere. Otto vox B.\eyer. 



Otto H.ahx. 



Berlin, Mav i. 



Peripatus papuens's. 



At the end of last June I received from Mr. A. E. 

 Pratt, the well-known naturalist, a number of fine speci- 

 mens of Peripatus which he and his son, Mr. F. B. Pratt, 

 had found in New Guinea on their recent expedition to 

 that island. This is the first time Peripatus has been 

 found in New Guinea. It was found by Dr. Willev in 

 New Britain in 1897, ^^^ by Mr. Muir and Mr. Kershaw 

 in Ceram last year (see Nature, July i, 1909, p. 17, and 

 Quarterly Journal of Microscopical Science, liii., igoq, 

 P- 737)- The New Guinea specimens were found in 

 January-, Februar>-, and March at Sara^-u, at an elevation 

 of 3^oo feet in the Central Arfak Mountains. Mr. Pratt, 

 in describing his discover}*, writes as follows : — " After 

 my son found the first specimen amongst the roots of the 

 grass, we at once show^ed it to the natives, offering them 

 a large knife (which is most valuable to them) for every 

 specimen. Quite sixty of the natives were searching for 



