August 26, 1909] 



NATURE 



26: 



tide, the /3 particle can be stopped ot entrapped by a 

 nioltcuie when travelling at a very high speed. 



When the great energy of motion of the a. particle and 

 the small amount of energy absorbed in ionising a single 

 molecule are taken into consideration, there appears to 

 be no doubt that the a particle, as Bragg pointed out, 

 actually passes through the atom, or rather the sphere of 

 action of the atom which lies in its path. There is, so to 

 speak, no time for the atom to get out of the way of the 

 swiftly moving a particle, but the latter must pass through 

 the atomic system. On this view, the old dictum, no 

 doubt true in most cases, that two bodies cannot occupy 

 the same space, no longer holds for atoms of matter if 

 moving at a sufficiently high speed. 



There would appear to be little doubt that a careful 

 study of the effects produced by the o or 3 particle in 

 passing through malter will ultimately throw much further 

 light on the constitution of the atom itself. Work already 

 done shows that the character of the absorption of the 

 radiations is intimately connected with the atomic weights 

 of the elements and their position in the periodic table. 

 One of the most striking effects of the passage of j3 rays 

 through matter is the scattering of the 5 particles, i.e. 

 the deflection from their rectilinear path by their encounters 

 with the molecules. It was for some time thought that 

 such a scattering could not be expected to occur in the 

 case of the o particles in consequence of their much greater 

 mass and energy of motion. The recent experiments of 

 Geiger, however, show that the scattering of the a par- 

 ticles is very marked, and is so great that a small fraction 

 of the o particles, which impinge on a screen of metal, 

 have their velocity reversed in direction and emerge again 

 on the same side. This scattering can be most con- 

 veniently studied by the method of scintillations. It can 

 be shown that the deflection of the a particle from its 

 path is quite perceptible after passing through very few 

 atoms of matter. The conclusion is unavoidable that the 

 atom is the seat of an intense electric field, for otherwise 

 it would be impossible to change the direction of the 

 particle in passing over such a minute distance as the 

 diameter of a molecule. 



In conclusion, I should like to emphasise the simplicity 

 and directness of the. methods of attack on atomic problems 

 opened up by recent discoveries. As we have seen, not 

 only is it a simple matter, for example, to count the 

 number of a particles by the scintillations produced on a 

 zinc sulphide screen, but it is possible to examine directly 

 the deflection of an individual oarticle in passing through 

 a magnetic or electric field, and to determine the deviation 

 of each particle from a rectilinear path due to encounters 

 with molecules of matter. We can determine directly the 

 mass of each o particle, its charge, and its velocity, and 

 can deduce at once the number of atoms present in a 

 given weight of any known kind of matter. In the licht 

 of these and similar direct deductions, based on a mini- 

 mum amount of assumption, the phvsicists have, I think, 

 some justification for their faith that they are building 

 on the solid rock of fact, and not, as we are often so 

 solemnly warned by some of our scientific brethren, on the 

 shifting sands of imaginative hypothesis. 



NOTES. 

 A MEETING of the permanent commission of the Inter- 

 national Association of Seismology will be held at Zermatt 

 on .August 30, under the chairmanship of Prof. .Arthur 

 Schuster, F.R.S. At this meeting reports will be presented 

 from a number of committees, appointed at the last general 

 meeting, which took place at The Hague in iqoy, and 

 questions of organisation will be discussed. Papers will 

 be read by Mr. H. F. Reid, on some lessons of the Cali- 

 fornian earthquake and a method of foretelling certain 

 earthquakes ; by Mr. Albert Heim, on the objects of earth- 

 quake investigations ; and by Prof. Palazzo, on a projected 

 seismic triangulation by means of wireless telegraphy. The 

 Central Government of the Confederation has charged the 

 Swiss Naturforschende Gesellschaft with the organisation 

 of the meeting, and arrangements have been made for the 

 NO. 2078, VOL. 81] 



accommodation of the delegates taking part in the con- 

 ference, who will also be able to travel on the railway 

 between Visp and the Corner Grat at half fares. 



On Tuesday next, August 31, at the ordinary fortnightly 

 meeting of the Royal Horticultural Society, Vincent 

 Square, S.W., there will be exhibited on behalf of Prof. 

 Sargent and the president and fellows of Harvard Uni- 

 versity, Cambridge, Mass., U.S.A., a selection of photo- 

 graphs illustrating the flora, fauna, and scenery of central 

 and western China. These photographs are from the large 

 collection taken by Mr. E. H. Wilson during his last 

 (third) journey to China. The exhibit will be of importance 

 to all who are interested in the recent new plant introduc- 

 tions from China ; it is also hoped that from its varied 

 chaiacter the selection made will appeal to a wider circle. 

 The photographs are whole-plate size (83X65 inches), with 

 liberal mounts for herbarium purposes, and all are labelled. 

 The work of developing and printing has been done by 

 the well-known worker in floral photography, Mr. E. J. 

 Wallis, of Kew. 



The preliminary mineralogical and geological survey of 

 Northern Nigeria, carried out under the auspices of the 

 Colonial Office and the Imperial Institute, has just been 

 completed by Dr. J. D. Falconer after five seasons' work. 

 ^'aluable deposits of tinstone have been located within 

 the Protectorate, as well as less important occurrences of 

 gold, argentiferous galena, monazite, and numerous ores 

 of iron. The economic results of the survey are being 

 issued as colonial reports by Prof. Dunstan, while the 

 scientific results will be published by Dr. Falconer in the 

 course of the coming winter. Important observations have 

 been made as to the age and origin of Lake Chad and 

 the Bauchi plateau, while suflicient data have been secured 

 for the compilation of a geological map of the Protectorate 

 which will largely fill up the existing blank in our know- 

 ledge of the structure of this portion of the Central 

 Sudan. 



Mr. Asquith announced in the House of Commons on 

 .August 19 that the Government has decided to recommend 

 Parliament to make a grant of 20,000!. in aid of the 

 expenses of Mr. Shackleton's expedition in .Antarctic 

 regions. Mr. Shackleton has informed a Press representa- 

 tive that this sum will meet all his guarantees. The total 

 cost of the expedition is said to have been nearly 45,000/. 

 Of this amount, 6000Z. was subscribed in Australia and 

 New Zealand, and the rest was provided by Mr. Shackle- 

 ton's friends. In a letter communicating the decision of 

 the Government to Mr. Shackleton, the Prime Minister 

 said : — " The Government have been induced to take this 

 course as they are much impressed both by the great value 

 of the discoveries made in the course of your voyage and 

 by the eflrcient and economical manner in which the whole 

 of the enterprise was conducted, as is shown by the 

 fortunate return of your entire party, and by the com- 

 paratively small total outlay incurred." 



We learn from Science of the death, in his eighty-third 

 year, of Dr. R. E. C. Stearns, known for his work on 

 the geographical distribution and variation of mollusca 

 and for other work in natural science. 



The death is announced, in his sixty-seventh year, of 

 Dr. Otto von Bollinger, rector of the University of Munich 

 and professor of general pathology and pathological 

 anatomy in the University. Prof, von Bollinger was the 

 author of a number of medical works, among them being 

 books on meat poisoning and on the heredity of diseases, 

 and the " Atlas und Grundriss der pathologischen 

 .Anatomic," which appeared in 1S96. 



