4o8 



KNOWLEDGE & SCIENTIFIC NEWS. 



[April, igo6. 



GEOLOGICAL. 



B)' Edward A. Martin, F.G.S. 



The New President of the Geological 

 Society. 



Sir AuriiiHM.D Geikik, whose recently published " l'"ounclers 

 of tieolotjV " we notice in another column, and who has 

 already lilU d the Presidential chair of the Geological Society 

 with ciistinctijn, has as^ain been elected as President for the 

 next two years, in place of Professor J. E. Marr, F.R.S., 

 who retires. 



Beneath the Earth's Crust. 



'I"he queslion which is beini;- discussed elsewhere in this 

 journal as to what is at the centre of the earth is of extreme 

 interest to geolog-ists, not solely on account of its bearing 

 on the problem of underground heat, but indirectly as 

 possibly affording some clue to the variations in climate in 

 past geological times. Geologists at one time did not 

 hesitate to ask that a change in the direction of the earth's 

 axis should be admitted, in order to explain the existence of 

 fossil tropical jjlants in what are now the frozen regions of 

 North .America, a fact now- apparently equalled by similar 

 discoveries in southern polar regions. Mr. De St. Dalmas' 

 contribution in " Knowledge " has usefully brought to 

 mind the great Halley's theory of a solid revolving nucleus, 

 although in his day' he coujd scarcely have realised the 

 bearing which, if proved to be correct, it would have on 

 future'geological science. Not only are we still with abso- 

 lutely lio clue to the cause of the existence of a magnetic 

 pole at all, but there is no satisfactory theory to account for 

 fossil vegetable life bearing a tropical facies in parts now- 

 bordering on .Arctic regions. Halley's theory that there is 

 practically a solid nucleus is accepted by most people. But 

 his theory that its axis is at an angle to that of the earth, 

 that its poles are the points towards which the needle dips, 

 and that the movements of the magnetic poles are caused 

 bv a swaving motion of its axis around our jioles, are points 

 which have entirely dropped out of consideration. 



R-efraction of Earthquake Shocks from 

 the Centre Core of the Ea.rth. 



'I'he c]ueslion of the constitution of the interior of the 

 earth, as revealed by earthquakes, has just been the subject 

 of a paper by .Mr. R. D. Oldham, F.G.S., which was read 

 at Burlington House before the (ieological Society. It is 

 particularlv interesting, in view of the discussion now going 

 on in our columns. The distant record, he says, of a 

 great earthquake exhibits three distinct phases, of which 

 the third represents w'ave-motion which has travelled along 

 the surface of the earth and is not dealt with in his paper, 

 as it can give no information regarding the interior of the 

 earth. The other two phases form the preliminary tremors, 

 and it is show-n that they represent the emergence of two 

 distinct forms of wave-motion, which have been propagated 

 through the earth. He thinks that the wave-paths 

 emerging at the greater distances have entered a central 

 core, in w-hich the rate of transmission of the first-phase 

 waves is reduced to about nine-tenths, and of the second- 

 phase waves to about one-half, of the rate in the outer 

 shell. The great reduction of rate in the case of the second- 

 phase w-aves means great refraction. 



Mr. Oldhim's researches lead to the conclusion that, 

 after the outermost crust of the earth is passed, there is no 

 indication of any niaterial or rapid change of physical condi- 

 tion, nor probably of chemical composition, until a de])th of 

 about six-tenths of the radius is reached ; but that, below 

 this, there is a rapid passage to matter which has very differ- 

 ent phvsical properties, if not also differing in chemical 

 constitution. Without advancing any hypothesis as to the 

 nature of this difference, he points out that it will have to 

 be reckoned with in any theory of the earth. In the dis- 

 cussion which followed, the President observed that there 

 could be little doubt that w-e were on the eve of important 

 additions to the data available for discussing the subject. 



At a meeting of the Geological Society on February 21, 



Miss Ethel M. R. Wood's paper on " The Tarannon .Series 

 of Tarannon " was read, the discussion being contributed to 

 by Miss Elles. Mr. G. E. Dibley exhibited a dental bone 

 of Cnninsatmis criissidi'iis (Dixon) from the Holastcr- 

 .•iuhfilobiisus zone of the chalk of Burhain, near Rochester. 



ORNITHOLOGICAL. 



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

 The PIun\age of the Shoveller. 



.\t the last meeting of the Ornithological Club .Mr. J. I.. 

 Bonliote exhibited a fine series of skins of .shoveller ducks 

 {Spatula chjpeata), illustrating the fact that this species 

 differed, so far as he knew, from all other ducks, in having 

 an intermediate plumage betw-een that of the " eclipse," the 

 full breeding plumage. 



Hitherto birds in this plumage had been regarded as im- 

 mature birds, but the difference between these and the 

 adults was shown unmistakably. Thus, in this inter- 

 mediate plumage the head is much darker than in the 

 " eclipse " dress, without metallic gloss, while the feathers 

 of the chest were white, with dark brown bars and a buff 

 margin. Young birds also assume this intermediate 

 plumage in their first year, but they may alw-ays be dis- 

 tinguished bv having the white feathers of the breast 

 spotted instead of barred. 



This peculiar dress succeeds the "eclipse" plumage in 

 September, and is gradually replaced by the full breeding 

 dress, which, however, is not completed until the end of 

 March. 



Hybrid Black Game. 



At this same meeting .Mr. W. P. Pycraft exhibited a re- 

 markably fine male hybrid betw-een black game and 

 pheasant, which had been shot at Ringford, Kirkcudbright- 

 shire. 



In this specimen the character of the males of both species 

 were about equally divided. The head, neck, and under 

 parts were of a rich glossy black with green reflections, but 

 the flank feathers show-ed traces of the mahogany red and 

 black characteristic of the pheasant. The peculiar notched 

 feathers of the neck and breast which obtain in the 

 pheasant w-ere w-anting The scapulars resembled those of 

 the voung blackcock, but the coloration of the back differed 

 from that of either parents. The tail was fan-shaped, 

 mottled with fine markings of black and brow-n, and with- 

 out bars. While the qnill feathers were like those of the 

 pheasant, the coverts, like the back, resembled those of 

 neither of the parents. The rump feathers were rounded in 

 shape, not pendant and discontinuous as in the pheasant. 

 .\s in the pheasant, the space around the eye was bare, 

 though the area was smaller than in the pure-bred bird. 

 The beak was of a pronounced pheasant type, but the 

 nostrils were feathered as in the blackcock. The legs 

 were feathered for about one-third the w-ay dow-n, but the 

 scaling below resembled that of the pheasant only in so far 

 as the outside of the low-er third of the tarso-metalarsus was 

 concfrned, the rest of the scales being hexagonal in shape; 

 while the comb-like fringe .-ilong the toes w-as conspicuous 

 by its absence. 



It is believed that this bird represents only the seventh 

 IvUown in-tance of the cross. 



Greenland Falcon in Antrim. 



In the Irish XntiiruUst for .March, Mr. Robert Patterson 

 records the fact that a male Greenland Falcon iFako 

 randicans) was shot on the top of the mountain called the 

 Knockagh, near Carrickfergus, on February 12 last. The 

 last record of this species in .Antrim was in 1865. 



Bittern in S. Wales. 



" G. W. V." writes lo the Fit Id (March 10) to .say that 

 when shooting in South Wales last month he |)ut u]> a 

 bittern, and shortiv after found another dead, " which had 



