Sept., 1905.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



229 



ORNITHOLOGICAL. 



By W. P. Pycraft, A.L.S., F.Z.S., M.B.O.U., &c. 



The Slaughter of Ravens and 

 Peregrines, 



The Field (July 29) contains a short account of the ruthless 

 persecution meted out to Ravens and Peregrines in Arg\'Ie- 

 shire, which is anything but pleasant reading. Though we 

 fully realise that these birds, if too numerous, are a menace to 

 farmers and game preservers, there can be no doubt but that 

 anything like a war of extermination is not only unjustifiable, 

 but foolish. The determination and ruthlessness shown by 

 the stalker on the occasion described by the writer are worthy 

 of a better cause ; and we are glad to note that he, too, con- 

 siders the incident regrettable. •' Surely," he remarks. " such 

 persecution as that of the raven and falcons might well be 

 stopped, at all events, in the breeding season. The sight of a 

 falcon on the wing is to many sportsmen a real pleasure, and, 

 in mv opinion, a few grouse might well be spared to them." 



Nesting of the Egyptian Plover. 



The remarkable nesting habits of the Egyptian Plover, 

 Pluviuins (B^yptius, have given rise to considerable discussion 

 during the last twenty years or so. The Field (August 5) 

 contains an interesting note on this subject, which may be 

 regarded as finally clearing up the matter. Brehm, it may be 

 remembered, stated that this bird buried its eggs in the sand, 

 where they were hatched, while Dr. Yon Heuglin, on the other 

 hand, said that he had always found them uncovered. From 

 careful observations of Mr. A. L. Butler, it would seem that 

 Brehm was right. His attention was drawn to the subject by 

 the apparently aimless wanderings of a pair of these birds on 

 a sand-bank on the Rahad River. At last one sat down, and 

 remained seated for nearly an hour. Flushing the bird he 

 endeavoured unsuccessfully to find the eggs. The next day 

 the bird came and sat on the same spot, and a second search 

 revealed two eggs about an inch under the sand. This was at 

 noon, and the sand was burning hot, hence he concluded that 

 the bird visited the eggs at about this time to shield them from 

 this excess of heat, the incubation being performed by the 

 heat of the ground. 



Hemipodes Breeding in Confinement. 



The value of the work done by the " aviculturist," is slowly 

 beginning to obtain recognition, and no one has done more to 

 bring about this change of opinion than Mr. D. Seth-Smith, 

 who has attained a series of quite remarkable successes in 

 inducing rare tvpes to breed in captivity. After much care 

 and trouble his endeavours to breed the variegated bustard 

 quail [Titrnix varia) have been rewarded, and he is to be con- 

 gratulated, for many new facts concerning the habits of these 

 birdsat this time have come tolight. In the Augustnumberof the 

 Avicultural Mai^azine he gives a long and extremely interesting 

 account of his observations. It has long been known that 

 among Turnices the females are the more brilliantly coloured, 

 and that as is the rule in such cases the male undertakes the 

 work of incubation, while the female does the courting. How 

 this is psrformed is particularly well told by Mr. Seth-Smith in 

 the article referred to. '' The male," he writes, " squats among 

 the grass, and the female runs round him. . . . with tail 

 more or less erect, and crop extended and carried close to the 

 ground. Having run round him once or twice she stands 

 facing him at a distance of about a foot. . . . and com- 

 mences ' booming ' or ' cooing ' to him like a cock pigeon, at 

 the same time stamping and scratching with her feet, while the 

 male responds with a faint clucking noise." Like the Tina- 

 mous, Mr. Seth-Smith believes these birds are polyandrous. 



A White Swallo>v. 



Mr. Henry Taylor records in the Field (August 12) the 

 fact that a white swallow is daily to be seen at his house at 

 Dyson's Wood, near Caversham. When it first appeared it 

 would seem that the swallows of the neighbourhood en- 

 deavoured to drive it away, but they have now apparently 

 grown used to its presence, and in no way molest it. 



Dartford Warbler Breeding in Sussex. 



The /ooloi^ist for August records the breeding of the Dart- 

 ford warbler at Maresfield, in Sussex, in May last, and the 

 birds appear to have been successful in rearing their young. 



Albino Starling. 



The Rev. Julian Tuck records the fact than an albino star- 

 ling was fhot at Beyton, in Suffolk, in June last. It had 

 apparently only recently left the nest. 



Dotterel in Rutland. 



The Field (June 3) records the occurrence, at Ridlington, of 

 seven Dotterel. Eitdronias ntinnelhis, which were kept under 

 observation in a field for halfanhour. " Mr. Horn," says the 

 writer, "previously saw the same number at Moscott on 

 May 21. 



PHYSICAL. 



By Alfred W. Porter, B.Sc. 



Professor Rutherford has been making further deter- 

 minations in connection with the particles emitted by radium. 

 Some of his results may be chronicled here. He finds that the 

 total number of .'\lpha particles expelled per second from one 

 gramme of radium bromide at its minimum activity is 3-6 X 10'" ; 

 and assuming that the composition of the compound employed 

 is Ra Br.>. it follows that the total number of Alpha particles 

 expelled per second from one gramme of rrTi/i»)» at its minimum 

 activity is 6'2 X 10'". Now the Alpha ray activity of radium 

 in radioactive equilibrium is four times this minimum value, 

 and includes three products — viz., the emanation, radium 

 A and radium C — which emit Alpha rays. Hence he con- 

 cludes that the total number of .^Ipha particles expelled per 

 second from one gramme of radium in radioactiveequilibrium is 

 about 2-5 X 10". This result is deduced from ihe current 

 produced in a nearly perfect vacuum when all electrons (which 

 carry a negative charge) were bent aside by a magnetic field. 

 The close agreement between this value and the value pre- 

 viously obtained from direct data based on the heating effect 

 of radium, and the observed volume of the emanation, leaves 

 now no room for doubt that the Alpha particles carry a positive 

 chargeatthemoment of their expulsion from the film of radium 

 salt, though at one time he was inclined to doubt that they 

 do. Accepting this conclusion, there is no obvious reason for 

 supposing that they are not charged at the moment of their 

 expulsion from the radium atoms themselves ; for it should 

 be noted that the film of radium bromide employed was very 

 thin. 



He has also determined that the number of Beta particles 

 expelled from one gramme of radium per second is about 

 7-3 X 10'° which is only a little in excess of the number pre- 

 viously obtained for radium at its minimum activity. The 

 results indicate that four Alpha particles are expelled from 

 radium in radioactive equilibrium for each Beta particle, and 

 thus confirm the theory of successive changes which Ruther- 

 ford has done so much to develop. 



If it be assumed that only one Alpha particle is expelled 

 during the disintegration of the radium atom then it follows 

 that the number of atoms which break up per gramme per year 

 is i'95 X 10"'. Taking the atomic weight of radium as 225, it 

 follows that about half a milligramme per gramme disintegrates 

 per year. It therefore takes about 1380 years for half the 

 radium present to be transformed. 



The Pendulum Accelerometer. 



Mr. F. W. Lanchester has devised an interesting apparatus 

 for measuring accelerations directly. It is clear that this might 

 be done by mounting on the moving object (e.i;., train or 

 motor-car) a spring balance, the mass being mounted so 

 as to permit of its horizontal motion only. The acceleration 

 of the mass (and therefore of the train) would be directly 



