2o6 



NA rURE 



[June 30, 1904 



insulating support in an exliausted vessel. An electroscope 

 is attached to the radium tube. Negatively electrified 

 particles are shot off by the radium, and penetrate the glass 

 tube, which is covered with a conducting coating of phos- 

 phoric acid, so as to act as an inductor. Thus a positive 

 charge is left, and causes divergence. When the electro- 

 scope leaf touches the outer vessel, which is earthed, it 

 collapses, and begins to charge up again. This will go on 

 so long as the radium lasts. — Demonstration of oscillating 

 electric discharges : Prof. A. Schuster, F.R.S., and Dr. G. 

 Hemsalech. The separation of the components of a slowlv 

 oscillating electric discharge is effected by blowing a steady 

 current of air through it. The discharge passes between 

 two slightly inclined metal plates, and spectroscopic analysis 

 shows the line spectrum of air in the initial discharge and 

 the band spectrum of nitrogen in the oscillations. The 

 metallic vapour from the electrodes does not seem to take 

 part in the oscillations. The effect of introducing cores of 

 iron or other metals into a coil giving self-induction may be 

 illustrated by this arrangement. — The thermo-galvanometer : 

 Mr. W. Duddell. The instrument is intended for the 

 measurement of very small rapidly varying currents such as 

 telephonic currents and the currents produced in the receiving 

 vertical wire in wireless telegraphy. The sensibility of the 

 instrument is such that either direct or alternating currents 

 from a few micro-amperes upwards can be measured. — .\ 

 new magnetic balance : Mr. \V. Hibbert. The beam of a 

 balance is made of a magnetised steel rod 27 centimetres 

 long. The " centres " of the poles are 25 centimetres apart. 

 'I'he repellent pole of a second magnet being placed over one 

 end of the beam causes this to descend, and the force of 

 repulsion is balanced by a weight sliding on the other half 

 of the beam. 



Photographs and diagrams illustrating solar and meteor- 

 ological changes, and a series of photographs to determine 

 the relative temperatures of the stars : Sir J. Norman 

 Lockyer, K.C.B., F.R.S. This exhibit included (i) enlarged 

 pictures of the sun in " K " light taken with the spectre- 

 heliograph of the Solar Physics Observatory. (2) Diagrams 

 illustrating the results of a discussion of sun-spot distribu- 

 tion ; the relationship between the positions of solar 

 prominences and the different forms of the corona ; the 

 different types, and their distribution, of the short-period 

 barometric pressure variation over the earth's surface; and 

 the close connection between the change of barometric 

 pressure and rainfall. (3) .Series of photographs taken with 

 a quartz-calcite prismatic camera of 2-inch aperture and 

 iS-inch focal length to determine the relative temperatures 

 of stars. (4) Composite positives on glass of the sun's limb 

 and disc, taken on the same plate with " K " light. — Photo- 

 graphs and drawings prepared from observations taken by 

 the lightning research committee to illustrate the behaviour 

 of lightning on certain buildings struck and damaged, not- 

 withstanding their being provided with lightning con- 

 ductors : Mr. Killingworth Hedges. — The physiotype : Mr. 

 Francis Sheridan. This is a method of permanent print- 

 ing without the use of inks, specially adapted to finger 

 printing and the reproduction of designs from animal and 

 vegetable life. The subject to be reproduced is pressed on 

 paper, and by dusting the invisible impression with a 

 coloured powder a dark and permanent print is produced. 

 — Experiment showing the effect of internal stresses in glass 

 upon light of different colours ; Dr. L. N. G. Filon. — Photo- 

 graphic camera with free-swinging lens, and photographs 

 taken with it : Dr. W. M. Flinders Petrie, F.R.S.— 

 (i) Photomicrographs of interior of a rifle barrel ; (2) photo- 

 micrographs of brass used for cartridge cases ; Dr. W. R. 

 Hodgkinson and Captain Hardcastle, R.A. 



K new automatic vacuum pump : Mr. C. E. S. Phillips. 

 The apparatus consists of a modified Toepler pump, so 

 arranged that it works automatically through the operation 

 of electrically controlled devices, for the purpose of pro- 

 ducing extremely high rarefactions. The pump will reduce 

 the gas pressure within a vessel of 200 c.c. capacity from 

 that of the atmosphere to 0002 mm. in fifteen minutes. — 

 Vibrograph for recording vibrations photographically : the 

 Cambridge Scientific Instrument Company, Ltd. The 

 instrument is essentially similar to that used by Mr. A. 

 Mallock, F.R.S., for recording vibrations caused by traffic 

 on the Central London Railway. — An experiment illustrating 

 harmonic undertones : Mr. H. Knapman. 



The origin and growth of ripple mark : Mrs. Hertha 

 Ayrton. The experiments shown illustrated the way in 

 which the sand ripples are formed on the sea shore. If 

 sand be spread quite evenly on the bottom of a trough, and 

 water above the sand be oscillated so as to produce stationarv 

 waves, a small ridge is formed where the horizontal velocity 

 of the water is greatest, ne.xt a ridge is started on each side 

 of the first, which grows ; then two more ridges are started, 

 the former growing, and so on until the whole surface of 

 the sand is ripple-marked. Each ripple now slowly moves 

 towards the place of greatest horizontal velocity, while fresh 

 ripples form near the places of least horizontal velocity. 

 Pairs of ripples then coalesce here and there, and finally 

 the greater part of the sand is assembled in a ripple-marked 

 heap at the places of greatest horizontal velocity, this final 

 result being attained, for example, in about twenty-five 

 minutes in the case of the six-foot trough exhibited, when 

 the stationary wave is twice the length of the trough. It 

 was also shown that ripples are not produced by a steady 

 current of water flowing over sand, but that by disturbing 

 this steady current sand ripples may be formed, which, 

 however, are erased on the current becoming, steady 

 again. 



Crystalline glazes on pottery : Mr. William Burton and 

 Mr. Joseph Burton. The specimens illustrated the decorative 

 application to English earthenware and stoneware of certain 

 recently discovered glazes which develop artificial crystalline 

 silicates during the firing and cooling of the wares. In 

 the " sunstone " and " fiery " crystalline glazes the crystals 

 have the optical properties of micas, though their exact 

 composition is at present undetermined. In the starry and 

 opalescent glazes the radiating needles are akin to the 

 mineral willemite, as is shown both by their optical proper- 

 ties and their composition. — Photographs of volcanic pheno- 

 mena in the Lipari Islands : Dr. Tempest Anderson. The 

 photographs, which were taken by the exhibitor in .\pril 

 of this year, show, besides the topography of the craters, 

 several changes which have taken place in and about them 

 since a former visit in 1888, and also some explosions from 

 the crater of Stromboli which took place while Dr. Anderson 

 was on that mountain. 



Mimetic resemblance of the different forms of a single 

 species of butterfly to two or three different models. 

 Seasonal phases of South African butterflies of the genus 

 Precis : Prof. E. B. Poulton, F.R.S. The fact that the 

 non-mimetic male of the South and East African Papilio 

 diinlamis possesses three different forms of female, each 

 mimetic of a different species of Danaine butterfly, was dis- 

 covered by Mr. Roland Trimen, F.R.S. Within the last 

 few months this discovery has for the first time been con- 

 firmed by breeding. The exhibited specimens, constituting 

 the entire evidence thus obtained, were bred by Mr. George 

 F. Leigh at Durban, Natal. • The evidence of the wonderful 

 seasonal changes in South African butterflies obtained by 

 Mr. Guy A. K. Marshall has been further increased during 

 the present year. His recently obtained evidence was ex- 

 hibited, and consisted of a wet-season female of Precis 

 nniilopc with its five dry-season offspring. — Colour photo- 

 graphs (Sanger-Shepherd process) of living moths and 

 butterflies in their various stages of larva, pupa and imago : 

 Mr. F. Enock. — (i) Living specimens of young flatfish; (2) 

 methods of determining the age of plaice ; (3) charts illus- 

 trating the natural history of the plaice in the North Sea ; 

 (4) charts illustrating the plankton and hydrography of the 

 English Channel during 1903 : the Marine Biological 

 Association. — The cilioscribe. a machine to record the move- 

 ments of cilia and the effect of physical conditions and 

 chemical reagents upon them : Dr. \V. E. Dixon and Mr. O. 

 Inchley. — Specimens of West Indian fire-flies : the Zoological 

 Society of London. 



Photography of the movements of plants by means of the 

 kammatograph : Mrs. D. H. Scott. The photographs are 

 taken at intervals varying according to the rapidity of the 

 movements of the plants during several days, and sometimes 

 weeks. They are then shown on the screen in the kammato- 

 graph, and the movements of many days can be followed in 

 a few seconds. — Models to illustrate the reduction (hetero- 

 tvpe) divisions in animals and plants: Prof. J. B. Farmer, 

 F.R.S., and Mr. J. E. S. Moore. 



(i) Model of the external door of the Great Pyramid ; 

 (2) ellipsograph : Mr. R. Inwards. 



NO. 1809, VOL. 70] 



