February j9, 19 12] 



NATURE 



605 



time to disappear. The genus is essentially African. Only 

 two or three so-called '■ species " of Rhipicephalus occur 

 out of Africa, and their distribution is easily accounted for 

 bv the fact that they are dog parasites. The other prin- 

 cipal Ixodid genera are well distributed all over the world. 

 — Prof. Nuttall : The parasites of equine biliary fever. 

 Prof. Nuttall described the two species of parasites, Piro-- 

 plasma caballi and Nuttallia equi, which occur in equine 

 biliary fever in .Africa, Asia, southern Europe, and South 

 America. It has hitherto been supposed that biliary fever 

 is due to but one species of parasite, but studies carried on 

 in conjunction with Mr. C. Strickland have demonstrated 

 that two diseases, due to distinct parasites, have hitherto 

 been confused under one name. Both parasites are very 

 deadly in their eifects ; they are transmitted from horse to 

 horse by ticks, and the blood of animals which have 

 recovered from all symptoms of the diseases remains 

 infective for years. 



Manchester. 

 Literary.- and Philosophical Society, February 6. — 

 Prof. F. E. Weiss, president, in the chair. — William 

 Burton : Note on the earliest industrial use of platinum. 

 The author gave an account of the general history of the 

 mineral, particularly its use for coating pottery, and he 

 exhibited specimens of pottery illustrating the application 

 of various metals. — Prof. E. Rutherford : The origin of 

 the P rays from radio-active substances. He stated that 

 from a study of radio-active transformations it has been 

 found that each atom of matter, in disintegrating, emits 

 one a particle expelled with a definite velocity, which is 

 characteristic of the substance. In many transformations, 

 j3 and y rays are emitted, and from analogy it would be 

 expected that one /3 particle should be emitted for the 

 transformation of each atom. The experiments, however, 

 of Baeyer, Hahn, and Miss Meitner, and of Danysz, have 

 shown that the emission of ;8 rays from the radio-active 

 substances is, in most cases, a very complicated pheno- 

 menon. The complexity of the radiation is most simply 

 shown by observing in a vacuum the deflection of a narrow 

 pencil of ;8 rays by a magnetic field. If the rays fall 

 normally on a photographic plate, a number of sharply 

 marked bands are observed, indicating that the rays are 

 complex, and consist of a number of homogeneous sets of 

 rays, each of which is characterised by a definite velocity. 

 The remarkable complexity of the ;3 radiation is well 

 instanced by the experiments of Danysz, who found that 

 the products of radium B and C together emitted at least 

 twenty-seven sets of homogeneous rays. Some of these 

 had a velocity e.xceedingly close to that of light. Notwith- 

 standing this apparent complexity, general experiments 

 have shown that the number of 3 particles emitted from 

 radium B and C is about that to be expected if each atom 

 in breaking up emits only one ;3 particle. In order to 

 explain this complexity of the )3 rays, it is necessary to 

 suppose either that the atom breaks up in a number of 

 distinct ways, each of which is characterised by the emission 

 of rays of definite volocity, or that the energy of the 

 )3 particle can be reduced by certain definite amounts in 

 its escape from the radio-active atom. The latter view 

 appears more probable and more in accordance with the 

 facts observed. It was found from an analysis of the 

 results given by Danysz that certain relations existed 

 between the energies of the individual /3 particles com- 

 posing some of the different sets of rays. The difTerence 

 in the energies of the particles from radium B and from 

 radium C could be expressed by a relation of the form 

 pa+qb, where a and b were definite constants and p and q 

 had integral values o, i, 2, 3, &c. This result may be 

 f-xplained by supposing that the jS particle initially is 

 liberated within the atom endowed with a certain speed, 

 but that in escaping from the atom it may pass through 

 two or more regions in which the quantity of energy a or b 

 is abstracted. The number of these units of energv 

 abstracted will vary from atom to atom, each individual 

 atom probably giving rise to only a few of the types of 

 rays observed. Evidence was given that the values 

 a and b served as a measure of the energy of the y rays 

 f-mitted from radium, and were connected with the energy 

 of the /8 particle required to excite the characteristic radia- 

 tions in the atoms of radium B or C. Prof. Rutherford 

 said that it is of great theoretical importance to examine 



NO. 2209, VOL. 88] 



with the greatest care the nature of the emission of /3 rays 

 from all the known radio-active substances, for it promises 

 to throw a great deal of light on the interior structure of 

 the atom. 



Dublin. 

 Royal Irish Academy, February 12. — Dr. R. F. Scharff, 

 vice-president, in the chair. — Rev. W. J. Ryan and 

 T. Hallissy : Some new fossils from Bray Head, 

 CO. Wicklow. This paper records the discovery, by the 

 authors, of new fossils at Bray Head, co. Wicklow, in the 

 formation known as the Bray and Howth series. .As the 

 field-relations of these beds to the adjoining altered shales 

 are obscure, different opinions have been held by geologists 

 as to their stratigraphical position in the geological series, 

 and owing to the absence from the formation of well- 

 recognised type-fossils, it has hitherto been impossible to 

 tix Uie age ot the rocks with any degree of certainty. The 

 importance of the recent discovery lies in the possibility 

 that the new fossils may possess a zonal value such as 

 may finally settle this interesting question. Mr. Cowper 

 Reed, who examined some of the fossils, thinks they 

 suggest the head-shield of a large trilobite like Soleno- 

 plciira howleyi from the Cambrian of Conception Bay, 

 Newfoundland. Other fossils found closely resemble 

 Walcott's holothurians, Eldonia ludwigi and Louisella 

 pedunculata, from the Middle Cambrian Burgess Shale 

 (Stephen formation), British Columbia. The authors infer 

 that it is highly probable that the green and purple slates 

 of Bray Head in which these fossils have been found must 

 b? referred to the same horizon of the Middle Cambrian 

 as the Burgess Shale of British Columbia. — R. A. P. 

 Rogers : Some differential properties of the orthogonal 

 trajectories of a congruence of curves. The family of 

 curves defined by ldx + mdy + ndz = o are envelopes of 

 " normal curves," i.e. those having /, m, n for normal at 

 each point of space. Dupin's theorem, Darboux's reci- 

 procal theorem, &c., are special cases of two simple rela- 

 tions connecting "normal torsions." The effect of 

 inversion on normal torsion. The indicatrices of torsion 

 and of curvature, and the relation between them. Ex- 

 pression of the condition of integrability as a relation 

 between normal torsions. The indicatrix of form. Ex- 

 pression of the Curl-vector and Divergence by torsion, 

 curvature, and the magnitude and direction of the gradient 

 of the original vector. Second type of generalisations of 

 Dupin's theorem, &c., arising from double generalisation 

 of lines of curvature (Voss's Kriimmungslinien and HatipU 

 kriimmungslinien). — S. B. Kelleher : Poisson's equation 

 and the equations of equilibrium of an elastic solid when 

 the surface displacements are given. 



BOOKS RECEIVED. 



Farmers of Forty Centuries, or PermanfMit Agriculluro 

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Elements of 1 hysiological Psychology. By Profs. G. T. 

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Kaiserliche .Akademie der Wissenschaften. .Atlas 

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Carnegie Institution of Washington. Year Book No. 10, 

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The Methods of Petrographic- .Microscopic Research. By 

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F"eeding Experiments with Isolated Food-substances. By 

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The Absorption Spectra of Solutions of Comparatively 

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A New Algebra. By S. Barnard and J. M. Child. 

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An Introduction to British ( l.i\-, Sh:il. ■,, ,iiul s.inds. 

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