December 22, 1898] 



NATURE 



191 



fererce to the earth. The paper contains sohilions of three 



oblenis which are concerned with the etlect of gravity on the 

 ^tlocity of propagation of elastic waves in the earth. The first 

 ! id second are based on a paper of Lord Rayleigh's ( Proceed- 

 it^'s, vol. .wii.). They show that when the wave-length is short 

 nough for us to consider the earth as bounded by an infinite 

 lane, the effect of giavity must be small. The third deals 

 'ith the vibrations of an elastic sphere under its own gravity ; 



;re the modification appears to be considerable, when we con- 

 der the appro.\iniate elastic constants of the earth. This case 

 partly founded upon a paper by Prof. Lamb (PrOieediiigs, vol. 



ii.) on the vibrations of a sphere. The author finds that the 

 p'fect of gravity is necessarily null when the order of the harmonic 

 ssturbance is zero or unity. For a sphere of the mass, size and 

 ■•avity of the earth, but with rigidity about that of steel, he 



ids the gravest free period to be 55 minutes ; without gravity 

 Me corresponding free period is 66 minutes. If the rigidity is 



30ut that of glass, the period is 78 minutes; without gravity, 

 '-20 minutes. The solids throughout are supposed to be incom- 

 iressible in order to avoid the difficulties introduced by gravity. 



-Lieut. -Colonel Cunningham (Mr. Tucker, f>ro tern., in the 



lair) drew attention to the three following e.xceptionally high 

 iiimbers : — 



j'l, N, = [22i3.(2=»0 + I)' IF (2=" ± 1)''J = (2''« ± I){2^'» + I)' 

 N3 = [l(2"'^-F I',-' -2™.(3.2'«+ l)\-' 



+ 1(2"'= + lY - 2--'-.(2"'« -1- 3)1=] = 2.(2-» + if. 



.he complete factorisation of the number's (2"" ± i) being 

 ,nown (see Lucas's memoir " Sur la Serie recurrente de 

 I'ermat," Rome, 1879, pp. 9, 10), the three large numbers (N) 

 je also completely factorisable into their prime factors. The two 

 [,, N„ are of order a*'", and therefore contain 253 figures; 

 'hilst N3 is of order 2*", and therefore contains 254 figures, 

 the largest number hitherto completely factorised into its prime 

 :!ctors (so far as known to the author) is (2-'"' -f I), which 



mtains 64 figures. 



Geological Society, December 7. — W. Whitaker, F. R.S., 

 'resident, in the chair. — The geological structure of the 

 Southern Malverns and of the adjacent district to the west, by 

 "rof. T. T. Groom. The structure of the district is explained on 

 .le supposition that the rocks represent the western margin of 

 'n old mountain-chain overfolded towards the west ; iheeastern 

 : ortion of this range lies faulted down and buried beneath the 

 'ermian and Mesozoic of the vale of Gloucester. All the 

 haracteristics of a folded chain are present, namely, the pro- 

 iund folds, overfolds, thrust-planes, and transverse faults; and 

 1 typical Austonungs-zone is seen to the west. — The Permian 

 'nnglomeratesof the Lower Severn basin, by \V. Wickham King, 

 "he rocks thus described are the calcareous conglomerates in- 

 luded in the Middle Permian of the Shropshire type, and ex- 

 |osed north of the Abberley and Lickey Hills. Three calcareous 

 (Orizons occur, interstratified in sandstones or marls, and 

 armounted by the F'ermian breccia. It was the opinion of 

 Umsay and others that the materials of the calcareous horizons 

 nd of the Permian breccia had been brought from the Welsh 

 torder ; but Buckland and Jukes, among others, claimed a 

 buthern derivation for those of the Permian breccia, from local 

 lill-ranges to the south. The latter view accords with the fact 

 'lat the pebbles composing these calcareous horizons, and also 

 Oe broken fragments constituting the Permian breccias north 

 if the Abberley and Lickey Hills, are coarser in the south 

 flsterly direction, and gradually become finer to the north-west 

 fhe fragments embedded in the Middle Permian calcareous 

 lands near the Lickey are chiefly of Archrean rocks ; but in 

 31 the other districts described there are very few rock-frag 

 lents older than Woolhope Limestone. On the other hand 

 Jebbles of dolomitic Wenlock and Carboniferous Limestones 

 ■-/re abundant, while Aymestry Limestone, Old Red, Carbon 

 'erous, and Lower Permian sandstones occur in greater or less 

 bundance : and all these rocks, except the Carboniferous 

 Limestone, may be seen in sitn near at hand to the south. 

 j| Entomological Society, December 7. — Mr. R. Trimen, 

 ;1'.R.S., President, in the chair. — Mr. McLachlan exhibited a 

 pries of specimens of the neuropterous genus Tetracanthagyna, 

 e Selys, including a pair of a new species from Borneo, which 

 /as the largest known of all recent dragon-flies, though it was 

 lightly exceeded in wing-area by the much more slender 

 \legaloprepiis caenulatus, a conmion Central- American species. 

 ]-Mr. A. II. Jones showed about sixty species of Lepidoptera, 



'i NO. I 52 I, VOL. 59] 



» 



taken round electric lights at Zermalt in August. — Dr. Dixey 

 exhibited a series of Pierid butterflies from the Neotropical 

 region to show the existence among them of seasonal forms. 

 The President observed that the exhibit was of special interest, 

 as affording the first recorded evidence of the existence of 

 seasonal dimorphism in Neotropical butterflies. — Mr. Ci. T. 

 Porritt exhibited an extraordinary variety of Bomliyx qurrciis, 

 bred in June last by Mr. W. Tunstall, from a larva found near 

 Huddersfield. The specimen was a female of deep chocolate 

 colour, with the band very faintly traced in dark olive. — Dr. 

 Chapman, Mr. Lloyd, and Mr. Nicholson exhibited butterflies 

 taken by them in Norway from June 20 to July 22, during the 

 past summer at latitudes 60^ 12' and 69° 50'. — Papers were con- 

 tributed by Mr. R. McLachlan, entitled " Considerations on the 

 genus Telracantlia^yna" ; by Mr. M. Burr, entitled "A List 

 of Rumanian Orthoptera " ; and by Mr. J. H. Leech, on 

 " Lepidoptera Heterocera from China, Japan and Corea. " 



Zoological Society, December 13. — Prof. G. B. Howes, 

 F.R.S., \'ice President, in the chair. — A communication was 

 read from Mr. H. H. Brindley, on certain characters of the 

 reproduced appendages in the Arthropoda, particularly in the 

 Blattida:. It was a continuation of a paper published in the 

 Proceedings of the Society for 1897 (p. 903), and contained 

 observations on the process of regeneration of the legs in the 

 Blattidse. — Mr. W. P. Pycraft read the second part of his 

 contributions to the osteology of birds, which dealt with the 

 Penguins (Impennes). The author found it necessary to divide 

 this on^er into six genera. Of these Eudyptula appeared 

 to represent the least specialised form of the whole group, 

 and probably came nearest to the ancestral stock. The 

 Impennes, as a whole, appeared to be most nearly related to the 

 Tubinares. It did not seem possible to distinguish the skeleton 

 of Catarractes pacliyrhynchiis from that of C. chrysocome. — 

 One of the most important features of this paper related to the 

 "secto-pterygoid," which the author described at some length. 

 — Mr. W. L. H. Ouckworth read a note, illustrated with 

 lantern slides, on a specimen of a female anthropoid Ape 

 which had been received from the Gaboon early in the present ■ 

 year, and as to which he was unable to decide whether it was a 

 Gorilla or a Chimpanzee. — Mr. J. Stanley Gardiner read a 

 report on the Turbinolid and Oculinoid Corals collected during 

 his recent expedition to the South Pacific. Nine species were 

 treated of in the paper, of which four were described as new. 

 — Mr. L. .A. Borradaile read the third instalment of a paper oi> 

 Crustaceans from the South Pacific. — Dr. G. II. Fowler con- 

 tributed the seventh of a series of papers on our knowledge of 

 the Plankton of the Faeroe Channel. It dealt with the Station- 

 data of depth, temperature, iStc , of the hauls of H.M.S. 

 Research in 1896 and 1897, with the chief Protozoa and Medusse ■ 

 of the collections. 



Edinburgh. 



Royal Society, December 5. — The Rev. Prof. Flint ir> 

 the chair. — The Chairman gave a short opening statement, re- 

 ferring, amongst other things, to the Antarctic Expedition, to 

 the survey of Christmas Island, to the new expedition to 

 Socotra, and to Dr. Traquair's important memoir of the pre- 

 ceding session, and concluding with short biographical notices 

 of recently deceased Fellows. — Prof. Kuenen, in a paper on 

 the miscibility of liquids at different temperatures, pointed out 

 the necessity of taking the vapour into account in the discus- 

 sion of any case of equilibrium. The mixtures dealt with were 

 chiefly mixtures of hydrocarbons and alcohols. In the case of 

 ethane and ethyl alcohol, the solubility curve was shaped like 

 a perverted 8— the vapour and upper liquid line joining at the 

 higher temperature, the two liquid lines joining at the lower 

 temperature. A few degrees above the lower temperature at 

 which the two liquids began to exist in equilibrium, it was 

 possible, by moderate increase of pressure, to get the liquids 

 to mix completely again. On the other hand, above the higher 

 temperature at which phenol and water began to mix in .all 

 proportions, a large increase of pressure caused a separation 

 of the liquids. — Prof. Ewart, in a paper on reversion in birds 

 and mammals, discussed many instances of reversion either to 

 a recent ancestor or to a remote ancestor. The influence of in- 

 breeding as establishing prepotency in one or both of the parents 

 was clearly shown, a prepotent parent or ancestor preventing 

 reversion. Prof. Ewart illustrated his remarks by means of 

 living specimens of pigeons and rabbits, and threw on the screen 

 views of the zebra hybrids with which he had been experiment- ' 



