304 



KNOWLEDGE & SCIENTIFIC NEWS. 



[December, 1905. 



A New British Shrike. 



At the meeting of the British Ornithologists Club held on 

 October 18, Mr. M. J. NicoU exhibited a fine male adult speci- 

 men of Latins iiiibiius, which had been killed at Woodchurch, 

 Kent, on July 11, 1905. 



BlaLck eared Chat in Sussex. 



At the meeting of the Ornithologists Club just referred to, 

 Mr. M. NicoU also exhibited a black-eared chat {SaxUola 

 sfapazimi), which had been killed at Pett, in Sussex, on Sep- 

 tember 9. This bird, Mr. Nicoll pointed out, belonged to the 

 Eastern form of the species, having the underside of the 

 wing and the axillaries jet black. The two previous occur- 

 rences of the black-eared chat in these islands were both of 

 the Western form (Sa-xicoln catarimc). 



Aquatic Warbler in Sussex. 



Mr. Nicoll also exhibited at this meeting an aquatic warbler 

 (Acrociphalus itiiuiilicus) which he had shot at Kye, Sussex, on 

 August iS of this year, and reported that during the day he 

 saw about half-a-dozen of these birds in one large reed-bed. 



Aquatic Warbler in Hampshire. 



Mr. H. F. Witherby exhibited at the meeting of the Club 

 just referred to, an acjuatic warbler which had been taken on 

 St. Catherine's Lighthouse, Isle of Wight, on September 29 

 last. The bird was an immature female, and made the third 

 record of this species in the county. 



Icterirve Wa.rbler in Hampshire- 

 Mr. Witherby exhibited, with the a<iuatic warbler, an im- 

 mature female of the icterine warbler (Hy/yotais icUrina). This 

 bird had also been taken on St. Catherine's Lighthouse at 

 the same time as the aquatic warbler, and was the first re- 

 corded instance of the occurrence of this species in the 

 county of Hampshire. 



^^^^^.^ 



PHYSICAL. 



By .-\li-rel) W. Porter, B.Sc. 



Emission of Corpuscles in the Dark. 



It is well known that the alkali metals give out negative 

 corpuscles ii.i-., electrons) when exposed to light, even when 

 this is of verj' feeble intensity. Thus in the case of sodium or 

 potassium or their liquid alloy, Mister and Geitel found that 

 a negative charge was dissipated by the light from a petroleum 

 lamp; while from the still more electro-positive metal rubidium 

 negative electricity could be discharged by the light from a 

 glass rod just heated to redness. The order of the metals for 

 this effect is the same as the order in Volta's series for contact 

 electricity. 



Professor J. J. Thomson has now shown that, with the 

 metals mentioned, there is a small emission of corpuscles, 

 even when all external light is excluded. .An electroscope is 

 placed in a bulb, which can be very highly exhausted by means 

 of charcoal cooled to a ver>- low temperature — the brilliant 

 device of Sir James Dewar for very rapidly producing exceed- 

 ingly high vacua. Clean rubidium or K-Na alloy is placed 

 below the gold leaves, and the metal is earthed. The whole 

 is placed in a light-tight case, no light being admitted except 

 a momentary illumination through a red glass window for the 

 purpose of reading the deflection of the leaves. Even this 

 momentary illumination produced a slight leak, which can, 

 however, be separated from the true leak by the fact that the 

 latter is proportional to the interval between the readings, 

 whereas the former is independent of this interval. 



When the leaves of the electroscope were charged with 

 po.>tlive electrification, there was always, even in the dark, a 

 small leak of electricity, while there was no leak when the 

 leaves were nei^ativdy charged. The leak apparent in the 

 former case is attributed to negative corpuscles leaving the 

 alkaline metal and settling on the leaves. This is proved by 

 the fact that when the bulb is placed in a transverse magnetic 

 field the leak stops. 



The presence of a minute quantity of hydrogen in the bulb 

 has an extraordinary influence in increasing the leak ; in some 



cases after the admission of the hydrogen, it was made 

 ten times as great. This increase rapidly died away, but was 

 renewed on admitting a fresh supply of hydrogen. No increase 

 was produced on admitting carbon dioxide. 



Final Disintegration Product of Radium. 



Rutherford considers that the ultimate residue alter all the 

 charged particles have been emitted by radium is lead. The 

 atomic weight of radium is 225 ; five .Alpha particles at least 

 are known to be expelled during the successive changes that 

 take place. If each of these is an atom of helium of mass 4 

 the residue must have an atomic weight of 205, which is ex- 

 ceedingly close to the atomic weight of lead. In support of 

 this conjecture, he cites the fact that in all radio-active 

 minerals lead is present, and its amount is roughly propor- 

 tional to the helium present. This would be the case if both 

 of them are disintegration products. 



ZOOLOGICAL. 



liy K. LVUEKKUR. 



Son\e Fossil R.eptiles. 



Since our last column of Notes was written three papers of 

 more than usual interest have appeared on extinct reptiles. 

 In the first of these Mr. C. W. Gilmore has published a brief 

 illustrated account of the complete skeleton of that most mar- 

 vellous of all fossil reptiles, the great horned dinosaur (Triccr- 

 atops prorsus) of the Cretaceous strata of Wyoming. In addi- 

 tion to its horns, the most extraordinary feature about this 

 creature is the huge size of its head, with its great frill-like 

 collar extending backwards well on to the shoulders. This is 

 shown by the fact that while the length of the entire skeleton 

 is 19 feet 8 inches, that of the head is no less than 6 feet, or 

 nearly one-third the total dimension. In this respect rnViT- 

 atops presents a strange contrast to the Diplodociis skeleton in 

 the British Museum, in which the head is only about one- 

 eightieth of the total length. Nevertheless, the horned monster 

 was no better off in the matter of brains than its small-headed 

 cousin. 



In the second of the two memoirs Mr. L. Dollo, of the 

 Brussels Museum, gives us the results of his investigations on 

 the footprints of the iguanodon, based on specimens from the 

 Wealden strata of Hastings and its neighbourhood. From a 

 careful study of these tracks the author is enabled to tell us 

 the approximate postures assumed by this giant dinosaur 

 when running, walking, and at rest. 



In the third and last paper Mr. Gilmore confirms the dis- 

 covery that the so-called toothless American fish-lizard, Dapta- 

 nodoii, really possessed a few rudimentary teeth, thus bringing 

 it into close relationship with Oplluiliiiosnurns of the Englisli 

 Oolites. 



The Deafness of Fishes. 



Despite the fact that carp in a pond will come up to be fed 

 at the sound of a bell, a learned German professor has arrived 

 at the conclusion that fishes of all kinds arc in all probability 

 stone-deaf. This conclusion, startling as it may seem, is 

 largely based on the fact that these creatures lack a certain 

 structure in their auditory organs which the professor regards 

 as absolutely essential to the function of hearing. Such vibra- 

 tions in water as fishes are capable of perceiving are conse- 

 quently believed to be transmitted by a sense compatible with 

 our own sense of touch or feeling. 



South America, Africa. at.nd Austratlia. 



In his recent presidential address to the Zoological Section 

 of the British .Association Mr. G. A. Boulenger, from the 

 evidence of freshwater fishes, is disinclined to believe in a 

 landcoTinection during late geological times between South 

 A.nerici and Africa. I'rofessor W. B. Scott, from the study of 

 certain fossil mammals, is, on the other hand, convinced that 

 such a connection did exist ; while the examination of some 

 supposed f(}ssil marsupials from Patagonia leads Mr. W. J. 

 Sinclair (who, like Prof. Scott, belongs to Princeton Univer- 

 sity) to be equally confident as to the existence of a similar 



