Shiteviuer, 1906 



KNOWLEDGE & SCIENTIFIC NEWS. 



545 



character, was enlivened owing to Mr. Swinburne havinLj 

 sent replies to possible speakers. These were read, and, 

 being in Mr. Swinburne's characteristic style, they helped 

 lo relieve the tension. 



Is an Alpha Particle Initially Uncharged ? 



'lliis qiicNlidii was the sulijirt ol .1 [i.iper at the Britisli 

 .Vs-suciatiun by Mr. F. Soddy. Several attempts have been 

 made previously to give a satislactory answer to it. VVhe;i 

 an .Alpha particle is ejected from radium emanation, does 

 it go away charged or is it at first uncharged, acquiring a 

 positive charge afterwards by impact with the particles of 

 air which it ionises ? It is certainly a most fundamental 

 question, because our views of the ultimate constitution of 

 matter are likely to be very dil'ferent according to the 

 character of answer given to it. Tremendous difficulties 

 meet the experimentalist in endeavouring to discover the 

 real state of things. It is essential that the Alpha particles 

 tested should have had no chance of colliding with other 

 matter before the test is made. This involves that they 

 shall be allowed to move only in the highest attainable 

 vacuum, and also that they shall be emitted from a radio- 

 active substance which is not more than one molecule thick. 

 The latter condition can be satisfied by dealing only with 

 the decomposition of radium C, which can be deposited in 

 a calculable amount upon the walls of a vessel. But the 

 attainment of a sufficiently high vacuum presents enormous 

 difficulties. In an ordinary Kijntgen ray vacuum, there are 

 probably still something like one hundred millions of millions 

 of molecules in every cubic centimetre, and even if the 

 vacuum can be pushed one hundred million times further, 

 there are still one million such particles [jresent ; so that an 

 .Alpha particle penetrating through one centimetre length of 

 such ;i " vacuum " would encounter one hundred molecules. 

 Mr. Soddy considers that he has sufficiently overcome this 

 difficulty. The test of charge employed by him is the 

 magnetic deviation of the .Alpha stream. Conditions were 

 arranged so that the stream was completely deviated under 

 ordinary conditions and, with the magnetic field excited, 

 did not succeed in escaping from the capillary tube in which 

 the active deposit of radium C had been laid ; and the 

 experiment consisted in testing whether any deviation 

 (arising from the supposed charge of the stream) took place 

 when the vacuum was made as high as possible. Long 

 series of results, all of which indicated possession of a 

 positive charge, led to successive improvements of the con- 

 ditions ; and, in the end, such conditions were obtained that 

 the stream uitderwent no deviation. The requisite condition 

 for obtaining this result seemed to be that the emanation 

 should be left for as short a time as possible in contact whh 

 the glass, which it gradually modifies, producing a black 

 deposit in it. If this result is accepted as unequivocal, the 

 conclusion necessary is that the Alpha particle is initially 

 LMicharged. Mr. .Soddy himself does not seem quite con- 

 fident in his explanation of the repeated failures, and until 

 any such doubt is cleared away it is premature to make 

 any revolutionary change in our conception of what goes on 

 in radio-active changes. There are undoubtedly diliUullii s 

 in either view. The great difficulty in considerinir the 

 charge as being possessed from the beginning of the isolated 

 life of the .Alpha ]xirticle, is that not only would the particle 

 take away a positive charge, but in many cases it also 

 leaves behind a positive charge. Now the' simultaneous 

 production of equal amounts of positive and negative elec- 

 tricity would seem to be as necessary as the simultaneous 

 production of two ends to a string in cutting it. Many of 

 us had thought that this difficulty had been completely 

 removed in the fairly recent discovery of slow moving 

 negatively charged emissions (already referred to in these 

 columns). It is well known that the characteristic electric 

 phenomena of radio-active change do not take place unless 

 the particles discharged have a velocity higher than a certain 

 critical one. .Any amount of discharge of negative electrons 

 may, therefore, be taking place without any sign of it being 

 delect.able by our rlniricd instruments. ' If the positive 

 .Alpha particle leaves b.liind .1 positive substance which 

 simultaneously emits slow moving negative electrons 

 (corresponding in some respects to the slow moving gases 

 which are ejected from a Roman Candle al the same time 

 as the b.all), the fund.imental laws of classical electricity 



will be satisfied. A similar explanation may of course be 

 made to account for the positive charge of the residue, even 

 if the Alpha particle goes away uncharged. But in this 

 case we have to account for the subsequent production of 

 a positive charge. If it acquires it from a gas molecule 

 which it ionises, the negative that remains must not be 

 forgotten ; any region completely through which a flight 

 of positive charges has taken place will be left negatively 

 charged, though to an amount which is at present too small 

 to be detecteii. The writer beli(;ves that .Mr. Soddy is of 

 opinion that his views are about to lead to an overthrew of 

 the fundamental laws of electricity. Mr. Soddy has, on 

 another occasion, suggested as much. The present writer 

 would urge all who are thinking about this subject never 

 to forget that it has been definitely shown experimentally 

 that in the sum total of radio-active charges which occur 

 inside a closed space, the total amount of electrification 

 produced is zero. 



ZOOLOGICAL. 



By R. Lydekker. 

 The Sleep of Animals. 



,Sl.N('K there is very liltle of gcner.d interest to record in the 

 matter of pure zoology, 1 \enlure to devote my first twj 

 paragraphs to subjects properly coming under the designa- 

 tion of physiology. Sleep is an attribute common to all 

 the more highly organised terrestrial animals (although 

 whether whales and dolphins ever slumber is still un- 

 known) ; and there are quite a number of mammals which 

 become torpid for a longer or shorter period, cither during 

 the drought and heat of a tropical summer, or in the cold 

 weather of the northern winter. .As regards the cause of 

 that suspension of consciousness which we call sleep, recent 

 investigations indicate the probability of the existence in the 

 brain of a " break-and-make " action. When the whole 

 apparatus in connected, the brain is in full working order; 

 when the disconnection is made, sleep is the "probable 

 result. The active working power of the brain lies in cer- 

 tain nerve-cells ; from these spring nerve-cords, which in their 

 turn divide and sub-divide till they terminate in small knobs 

 Formerly these nerve-cells were supposed to be in permanent 

 connection by means of their terminal branches ; but now 

 it appears thaf the terminations of these branches are onlv 

 in apposition, and are capable of being separated. The 

 fact that narcotic substances induce it is an almost con- 

 vincing proof that such separation is the immediate cause of 

 slumber. It is added by Sir William Gowcrs, who has lately 

 developed and explained the new theory, that by its means 

 we are readily able lo explain the phenomenon of sleep- 

 walking. 



Fish Out of Water. 



It IS well known that certain kinds of fishes are able to 

 li\e out of water much longer than others ; the power being 

 dependent upon the length of time that their gills are capable 

 oi rem.iining damp. So long as this condition lasts, fish are 

 able to obtain the necessary amount of o.xygen from the air 

 through the medium of the water spread over the fine mem- 

 brane of the gilis. Recently a German has invented <in 

 apparatus by means of which the gills can be kept moist for 

 an indefinite period. This apparatus consists of a wooden 

 box, with a number of compartments corresponding with 

 the size of the fishes. On the fioor of each compartment is 

 a layer, half an inch deep, of cloths saturated with water, 

 which by evaporation keeps the atmosphere moist. The 

 gills of the fishes are thus kept damp; while oxygen is 

 supi>lied from a receptacle outside the box. Many kinds of 

 fresh-water fish have, it is said, been kept alive for from 

 three to four days, by means of tliis ingenious in\ention. 



The Fossil Reptiles of Africa. 



Ihe (•Mirul nptH.-s of Soulh Africa .are .unong th<' most 

 vyond.Mlui m the whole world, and have .iltracled the atten- 

 tion and interest of a number of the most distin.-'uish&l 

 palaeontologists ; and well they may, seeing that thev in- 

 ■. ude among them the undoubted incestork of mammals 

 although this ancestral group is by no means confined to 



