2^,6 



NATURE 



[July i8, 1872 



which is overlain by dark -green sandy clay and Gault, turned up 

 at a high angle (and probably squeezed out) in the breadth of a 

 few yards, before the iron-sands are reached on returning to the 

 hUl-side. The party next came to the foot of St. Martha's Hill, 

 or Martyrs' Hill. Before mounting this hill of sand, seauied 

 irregularly with ironstone, some of tire geologists descended the 

 Halfpenny Hatch lane, leading down towards the East Shilford 

 bottom, and saw a section of sand and calcareous sandstone, 

 with a fuller's earth band and pebbly beds, similar to those in the 

 quarry on the other (western) side of Guildford. The under- 

 ground structure of South-Eastern England is connected with 

 that of the Boulonnais, of Belgium, the Ardennes, and West- 

 phalia ; and the folds and ridges of paheozoic rocks, that in 

 those countries bear up, cither at the surface or just beneath 

 the Chalk, or the attenuated Oolites, valuable coal-beds, are 

 continued through, in a broad sweeping line, underneath parts 

 of Surrey, Kent, and Sussex, until visible again near Frome, 

 in the Bristol coal-area, in North Devon, South Wales, and 

 the South of Ireland. The old faults and fissures affecting 

 this linear tract of old strata had long before the Coal-periud 

 raised and depressed tlie lands and sea-beds ; and, as a great 

 spur of the old Scandinavian lands, this tract afforded ground 

 for the littoral growth of the jungles that formed the coal on 

 its oscillating borders and in its lagoons, now shut up by bars, 

 and now losing their marsh features by influx of the sea. Suc- 

 ceeding ages still brought oscillations and changes, until the 

 Jurassic seas crept over this old ridge or shoal, and the Cretaceous 

 seas quite buried it, at first insands and ultimately by the calcareous 

 ooze of oceanic depths. But again another contracting crush of the 

 earth's crust operated on the old weak lines, and the buried ridge 

 slowly uprose, and its coaling of thick strata were worn off by sea 

 and rain, making pebbles and sand for the Lower Tertiaries ; and 

 still rising, it was at length laid bare in the Franco-Belgian and 

 the Bristol areas ; whilst our Wealden valleys of elevation, and 

 those of Kingsclere, Shalbourn, and Pewsey, show where its 

 uneven back approaches near the soil. 



SOCIETIES AND ACADEMIES 



London 



Royal Society, June 20. — "On the 26-day Period of the 

 Earth's Magnetic Force," by Mr. J. A. Broun, F.R.S. 



Referring to the Astronomer Royal's important communica- 

 tion on this subject, the author confesses that, projecting his 

 results for the horizontal force, he cannot agree in his final con- 

 clusions from them. In his paper he limits himself wholly to 

 the observations of the horizontal force, as he has found that 

 element, when aecurately corrected for temperature, best fitted to 

 show the period in question. 



As far as the existence of a period of near '.6 days is con- 

 cerned, he thinks there cannot be the slightest doubt ; the 

 examination of great masses of observations has confirmed his 

 belief ; but we know nothing certainly as to its cause. It appears 

 to be most probably connected with the sun's rotation ; but in 

 what way this may act nothing is known. The single periods 

 show great breaks, and what may be termed accih-ntal minima, 

 in opposition to the minima belonging to the period ; these acci- 

 dental are connected with great disturbance, probably allied to 

 the solar eruptions, or to causes which generally produce spots and 

 protuberances. We might suppose that the sun during its rota- 

 tion produces an action on the magnetic or electric ether in 

 motion, which, as far as it acts on our magnet, may be sup- 

 posed in greater quantity or mote condensed in certain parts of 

 the earth's orbit, and in certain years ; and, as has been sup- 

 posed in the case of the frequency of the solar spots, this ether 

 may also be acted on by the planet, and produce an irregularity 

 in the length of a few successive periods. These suppositions 

 are made merely to show that we are perhaps not in possession 

 of all the conditions of the problem, without which perfect 

 exactness in the calculations is impossible. 



In conclusion, he refers those interested in the subject to plate 

 xxvii. m the Transactions of the Royal Society of Edinburgh, 

 vol. xxii. where the daily means of horizontal force are projected 

 for four stations on the earth's surface, all of which agree in 

 showing the same movements, some of which have an amplitude 

 of '002 of the whole horizontal force (the Astronomer Royal's 

 result for 1870 gives a mean value of nearly the half of this), and 

 with intervals of about 26 days. 



Paris 

 Academy of Sciences, July I. — M. M. Marie read a 

 memoir on some general properties of the imaginary envelope of 

 the conjugates of a plane place. — M. H. Re-al comnrunicated 

 general equations of the movements of a solid body referred to 

 its movable axes ; and M. Montucci lorwardeianote describing 

 an experiment for the appreciation of the reiistance of a sheet of 

 brass to atmospheric pressure. — M. J. Bourget presented a memoir 

 on the mathematical theory of the movement of a cord, one of 

 the extremities of which possesses a given movement. — M. G. 

 Tissandier communicated a notice of an optical pnenomenon 

 observed during a balloon ascent, describing a case in which the 

 shadow of the bxUoon was thrown distinctly upon a white cloud, 

 and surrounded by a pale elliptical halo, exhibiting the colours 

 of the rainbow. — M. Faye communicated a letter from M. 

 Tacchini noticing the occurrence of magnesium in the chromo- 

 sphere of the sun. — M. J. A. Brown presented a note on the 

 simultaneity of barometric variitions between the tropics. — 

 General Morin commanicated an extract from a letter by M. 

 Vinson describing a severe cyclone which followed the aurora 

 australis of Feb. 4, 1872, at Reunion. — .M. W. de Fonvielle 

 gave an account of observations made during the ascents of the 

 balloon "Lea," in which he refers to the above-mentioned note 

 by M. Tissandier, giving the credit of the first observation of the 

 halo round the shadow of balloons to Mr. Glaisher, and especi- 

 ally to the oscillation and rotation of balloons. — M. L. Sollier 

 forwarded a note on the destruction of Phylloxera vastalrix by 

 means of a decoction of tobacco. — M. C. Bernard presente I a 

 fourth note by M. Paul Bert, on the inllnence exerted by changes 

 of barometric pressure upon the phenomena of life ; and M. 

 Wurtz communicated a third note, by M. Ore, on the question 

 whether strychnine is to be regarded as an antidote to chloral. — 

 M. Decaisne communicated an interesting paper by M.\I. Van 

 Tieghem and Le Monnier, "On the Polymorphism of the Re- 

 productive Organs in the mucorine genus MjrtiereUa." — .\I. 

 Leymerie presented a brief reply to a note by M. Garrigou on 

 the constitution of the Pyrenees. 



BOOKS RECEIVED 



English.— Town Geology ; Rev. C. Kingsley (Slrahan and Co.).— The 

 Life of Ri:hard Trevithick, vol, i. : F. Trevithick (E. and F. Spon).— Health 

 and Comfort in House Building: J. Drysdale and J. W. Hayward (E. and 

 F. Spon). — Nautical Surveying ; J. K. Laughton (Longmaoi). — Sewer Gas, 

 and how lo keep it out of Houses: O. ReynoU* (MacinUlan). 



Foreign.— Zeitschrlft fiir Biologic : Pettenkofer, Radlkofer, and Vogt, 

 B.and 7, Heft 3, 4, Band 8, Heft i.— Abhandlungen des Naturwissen- 

 schaftlichen Vereius zu Bremen, Baud 3, Helt i.— Die Echinoiden der 

 oesterreichis^h-hung.Trischen oberen Tertiarablagerungen : Dr. Laube. — 

 Die Erforschung des Silden-polar Gebietes : Dr. G. Neumiyer.— Zur 

 Kenntniss der ChlorophyllfarbestotTe : Dr. G. Kraus. — Jahrbuch der k. k. 

 peologischen Reichsanslalt zu Wien, Jan -March —Notizbjatt des Vereins 

 fiir Erdkunde : L. Ewald —Zur Morphologic des Saugethier-Schudels : Dr. 

 J. C. G. Lucae. 



CONTENTS PAoa 



MeOic.1l Education 217 



Ornithology of Nkw Zealand 2i3 



Our Book Shelp 220 



Letters to the Editor: — 



Spectrum of Lightning.— Henry R. Procter, F.C S 220 



The Aurora of July 7.-Rev. M. H. Close : J. Eu.mund Clarke 220 



Registering Thermometer. — Rev. Charles H. Griffith . . . 221 



Luminous Matter in the Atmosphere. — J.F.Anderson .... 221 

 Vibration of Glasses containing Effervescing Liquids.— Allen 



Beazeley.C. E 22 1 



The Names Cambrian and Silurian in Geology.— D. C. Davies . 222 

 On the Variation of Species as Related to their Geographi- 

 cal Distribution, Illustrated by the .\chatinellin.e. By 



John T. Gulick 222 



Evans's Stone Implements of Great Britain. II. {li'ii/'t lilus^ 



tratiotLs) ... 225 



Notes ... .... 227 



Prof. Agassiz's South American Expedition. II 229 



On the Sfectrum of the Great Nebula in Orion, and on 

 the Motions of some Stars towards or from the Earth. 



By Vl'iLUAM Huggins, F.R.S 231 



Excursion of the Geologists' Association to Guildford and 



Chilworth, June i 235 



Societies and Academies 236 



Books Received 236 



Errata.— Vol. v., p. 167, col. 8, 1. 20, for "sufficient from " read ,',' suffi- 

 cient heat from ;" p. 16S, col. i, 1. 11, for " inorganic " read "organic." 



