March, 1906.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



389 



on both sides of the Nile Valley, between Aswan and Esna 

 (lat. 24° to 255"). Far from the Cretaceous and Eocene 

 forni-ritions being here at all times unconformable with one 

 another, there is distinct evidence that the passage from the 

 oldest to the yoimgest beds was in some localities, notably 

 near Ain Amur, so gradual that near the junction, fossils 

 typically characteristic of Cretaceous beds in other places, 

 occurred side by side with forms having distinct Eocene 

 affinities. On the other hand, in the Baharia Oasis, the un- 

 conformity is most strongly marked. Of the Cretaceous 

 beds, Ihe Danian stage is clearly shown, whilst above these 

 beds, and below the Lower Libyan (Eocene), Mr. Beadnell 

 found it necessary to classify the Esna shales as passage 

 beds, some 197 feet thick, since they undoubtedly bridge 

 over the period which elapsed between the deposition of the 

 Cretaceous white chalk and the incoming of the Nummulitic 

 sea of Koctne limes. 



Ripple -Ma.rked Sa-ndstone Tiles. 



With a ijlc:ntiful supply of slatis and tiUs fur the roofing 

 of houses, the use of ripple-marked slabs of sandstone is not 

 now, perhaps, so noticeable as formerly. Formerly the 

 fissile slabs of Wealden sandstone, on which a long-ago in- 

 coming tide had left the impress of its rip|)les, were in great 



demand, and many of ihr uld.r Wr.iMcn faiinhouses may 

 be seen to be roofed willi them. The ilkustration shows a 

 farmhouse near Bletchingley, in Surrev, roofed with some- 

 what substantial sandstones, manv of which are very clearlv 

 ripple-marked. These may be of' Lower Greensand age. 



OR.NITHOLOGICAL. 



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

 Bird Migra.tion. 



The first Report of the Committee appoinlnl hv the British 

 Ornilhologists' Club lor ilie sludv of Ihe migrations of our 

 British birds has just been i)ublished, and forms an exceed- 

 ingly valuable contribution to our knowledge of this subject. 

 The work began early in 1905 when schedules were di.s- 

 Iributed among a number of willing workers in England 

 and Wales— lo which areas the observations are to be con- 

 fined for the present— and to numerous lighthouses and 

 lightships. Over 15,000 records were received, and the 

 report in question gives the results of the analyses of these. 



The work for this year was confined entirely to the arrival 

 and dispersal over the country of twenty-nine of our 

 commonest summer visitors— the warbler, swallow, swift, 

 nightjar, cuckoo, and land-rail being among Ihe number. 



It would seem from the report tiiat, in some species, at 

 any rate— as the whin-chat and chilfchall- the birds which 

 arrived first passed on northwards to nest, their place being 



taken by later arrivals; while the western and north- 

 western counties of England were populated before the 

 eastern and north-eastern. 



-Space, however, forbids a further summary of the results 

 of the first year's work, which is full of most interesting 

 facts, and should be read and studied bv all who are inter- 

 ested in this subject. The great feature of this admirable 

 digest are the maps which illustrate the movements of the 

 species dealt with. Those who desire to obtain copies of the 

 report should write to the publishers, Messrs. Witherby and 

 Co., High Holborn. 



Bittern in Essex. 



The Field, January 20, records the fad tliat a bittern was 

 seen within twenty-five miles of London on the nth of this 

 month. It was surprised by a sportsman in some sedgy 

 growth " surrounding a large piece of water " and was, to 

 his crcMlit, allipwcd lo escape unha'rmi-d. 



Ferrviginous Duck in Suffolk. 



I wo examples— sex not stated— according to the Firhl of 

 February 3 were shot during the end of January near Bury 

 .St. Edmunds. 



Wall Creeper at Ecclesbourne. 



At the l.ist meeting of the British Ornithologists' Club an 

 example of the wall creeper (Tkhodioma tnuiaria) was ex- 

 hibited which had been shot while climbing about the face 

 of the cliff at Ecclesbourne, near Hastings, on December 26, 

 iijoi. It proved, on dissection, to be a female. This makes 

 tile fi.urtli incurrence of this birti in (ireat Britain. 



Dusky Thrush in Nottinghamshire. 



At the meeting of the Club just referred to an example of 

 the dusky thrush (Turdus fiiscutiis) was exhibited, which 

 had been shot by a market gardener near (iunthorpe in 

 October, 1905. This makes the first recorded occurrence of 

 this bird in these islands. 



Fire-Crested Wren. 



There was ,ils,i rxliibilcl .1 ni.d.- example of the fire- 

 crestrd wren (llcialas iguicapillus), which had been shot at 

 Wimbledon, December 37, 1905. This marks the first oc- 

 currence of the bird in Surrev. Another example, also a 

 male, was exhibited by Mr. W.'R. Ogilvie (irani, which had 

 been picked up in a dying condition' at .\bbev Wood, Kent, 

 January 10, 1906. 



An Abnormal Eider. 



A more caiclul scrutiny of our eider ducks would seem to 

 show that occasionally at least specim<'ns occur with a 

 more or lees distinct V-shaped mark on the throat hitherto 

 supposed to obtain only in the Pacific eider. An example of 

 this kind w.-is exhibited at the meeting above referred to l)y 

 Mr. Howard Saunders, which had beei'i killed on December 7, 

 1905, near Stromness, Orkney. Whether this peculiar mark 

 is the result of a cross with the Pacific species which oc- 

 casionally occurs, in our waters, or is independently developed, 

 it is impossible at present to say. 



PHYSICAL. 



Hv Ai.iKi.i> W. I'oKn K. P..Se. 



Do Rontgen Rays Disintegrate Atoms? 



All substances when illtnninated by Kunls^eu rays or by 

 Becquerel rays of the ; type give out a complex secondary 

 radiation, part of which at least is wholly dift'ereut in character 

 froiu the primary radiation. For example, the secondary 

 radiation due to the absorption of Rontgen rays consists in 

 part of negatively charged corpuscles or electrons, although 

 no such charged particles exist in the exciting rays. This 

 suggests that there may be some breaking up of the substance 

 upon which the exciting rays impinge— a disintegration of the 

 same type as that which takes place spontaneously in radio- 

 active substances. On the other hand, the production of 

 streams of electrons by no means proves that such disintegra- 

 tion is a fact; for according to modern theories of electric 

 conduction there exist numerous electrons in a conductor — 

 and what substance is not a conductor ?— which are only 



