64 



NATURE 



[May 1 8, 1893 



range is from 0° to 620=C. (ijlSo'E.) ; the softening point of 

 the glass, a specially hard kind, being about 650°C. The 

 separate specimens of the alloy are exhibited to show its purity 

 and its very remarkable surface tension. 



Mr. Cecil Carus- Wilson exhibited the scotographoscope, for 

 enabling lecturers to demonstrate with chalk in a darkened 

 room. A compartment encloses a lamp so arranged as to 

 cast a pure white light upon the interior surface of the sheet of 

 specially prepared glass, which forms the front of the apparatus. 

 In a darkened room, on removing the sliding screen, an in- 

 tensely white surface is exposed, upon which chalks of any 

 colour can be used in the ordinary way. Small chalk drawings 

 easily seen at a distance of too feet or more, and they may be 

 rapidly deleted by means of a damp sponge. The whole 

 apparatus folds into a small compass for travelling. 



Magnetic curve tracers, were exhibited by Prof. Ewing, F.R. S. 

 The magnetic curve tracer exhibits the relation of magnetism to 

 magnetising force in iron. A mirror, which is free to move 

 both vertically and horizontally, receives two component 

 motions : one (horizontal) proportional to the magnetising 

 force H, and the other (vertical) proportional to the magnetisa- 

 tion B. The reflected light traces the characteristic cuve or 

 B and H, exhibiting the influence of magnetic hysteresis. The 

 instrument at work in the recess shows a cyclic process caused 

 by periodic rapid reversals of magnetising force. A more recent 

 form of the magnetic curve tracer is also shown (made by 



Messrs. Nalder Brothers) which is arranged for the commercial 

 testing of iron. The metal whose magnetic qualities areto be tested 

 is made up in rods, which are readily inserted and removed. The 

 rods which are shown are built up of narrow strips of sheet iron. 



Prof A. Smithells, B.Sc, exhibited experiments to demonstrate 

 the structure of flames. (l) The separation of a non-luminous 

 coal-gas flame into two combustion cones is effected by sliding 

 a wider tube over the one on which the fl.ime rests. The pro- 

 ducts of combustion can be aspirated from the intervening 

 space. (2) Using benzene vapour instead of coal-gas, the tran- 

 sition from a simple luminous flame to a non-luminous fla'ne is 

 shown. The two cones of the latter are separated as before, 

 and by a further addition of air the outer cone disappears, the 

 complete combustion occurring in a single cone. (3) By intro- 

 ducing a spray of a solution of a copper sail, it is seen that the 

 coloration of the flame occurs only in the outer cone where 

 copper oxide is formed. (4) The cone flames are also separated 

 by using a single tube. A platinum wire is pushed up axially 

 till it touches the inner cone. On drawing it down, the inner 

 cone is inverted and follows the wire. 



Rev. F. J. Smith, M.A., exhibited an inductoscript. The 

 inductoscript figures and pictures are made by placing the 

 object to be reproduced in contact with an ordinary photo- 

 graphic plate, placed upon a conducting sheet of metal. The 

 object and the plate are connected to the terminals of an in- 

 duction coil or other source of electricity, for a fraction of a 

 second, and then developed in the usual m.inner. Several of 

 the pictures shown were produced on plates which had been 

 exposed to full daylight. The pictures marked B were pro- 

 duced by the same method on bromide paper. Non-conductors 

 such as wood blocks are coated with a surface of plumbago 

 before being operated on. The best results are obtained by 

 conducting the process in oxygen gas under a pressure of about 

 two atmospheres. 



Platinum thermometers and pyrometers, compensated resis- 

 NO. 1229, VOL. 48] 



tance boxes and galvanometers, compensated barometer and 

 air thermometer, exhibited by Mr. H. L. Callendar ; a 

 series of sections illustrating the seasonal distribution of tem- 

 perature in sea- water lochs, exhibited by Dr. Hugh R. Mill ; a 

 portable hydrogen oil safety lamp, adapted for illumination and 

 delicate testing in air containing any kind of inflammable gas 

 or vapour, exhibited by Prof. Frank Clowes, D.Sc. ; tuning 

 forks worked electrically, a portable photometer, a table po- 

 lariscope, exhibited by Sir David Salomons ; high tension 

 apparatus, exhibited by Sir David Salomons and Mr. L. Pyke ; 

 electrical apparatus, exhibited by Major Holden. 



The Marine Biological Association exhibited marine inverte- 

 brata from the Plymouth area. Selected specimens of Crustacea 

 decapoda, and mollusca opisthobranchiata, including many rare 

 species, and illustrating the richness of the Plymouth fauna. 



Dr. G. H. Fowler exhibited specimens of oyster shells. The 

 specimens illustrate: — (l) The rate of growth of the oyster. 

 (2) Natural varieties of the shells. (3) Modifications of a 

 variety bred under new conditions. 



Prof. Weldon, F. R.S., exhibited diagrams showing the fre- 

 quency of variations in the size of certain organs of crabs. The 

 diagrams are based on measurements of portions of the carapace 

 and other parts of Carcinus vuanas. The organ to which each 

 diagram refers is indicated in the central drawing of a crab. 

 Each diagram is based upon measurements of 1,000 individuals, 

 and the size of the organ measured is indicated (as a percentage 

 of the body length) on the base-line of 

 each. The vertical ordinates of the black 

 curve show the number of individuals 

 having the organ measured of the given 

 ~ magnitude, and the red curve is a prob- 



ability curve. 



Spectra of the flame from a Bessemer 

 J converter, exhibited by Prof. W. N. 

 • Hartley, F. R. S. The photographs com- 

 prise the solar spectrum intended for 

 reference, together with spectra of the 

 Bessemer flame taken at consecutive 

 periods of the " blow " as indicated by the 

 time during which the plate was exposed 

 in each case. The flame spectra will be 

 seen to be composed of (l) a continuous 

 spectrum due to carbon monoxide ; 12) a 

 band spectrum belonging to metallic man- 

 ganese ; and (3) aline spectrum princijially 

 Lines of potassium, sodium, and manganese 

 Taken at the Crewe Works of the London 

 and North-Western Railway Company, by permission of Mr. 

 F. W. Webb, January, 1893. Enlarged ten diameters by the 

 Autotype Company. 



Prof. J. Norman Lockyer, F.R. S., exhibited the photo- 

 graphic spectra of some of the brighter stars. 



Mr. Isaac Roberts, F. R.S., exhibited five original negatives 

 and enlarged photographs of nebulae and clusters of stars, taken 

 with the 20-inch reflector by the exhibitor. 



Some species of butterflies, illustrating protective mimicry were 

 shown by Colonel Swinhoe. Mimetic forms of the nymphalid 

 genus Hypolimnas in India, Malayana and Africa, showing 

 the various phases of development of mimicry in two widespread 

 species of the same genus ; also mimetic resemblances to dif- 

 ferent protected species in the females of Euripus halt- 

 therses, &c. 



The Zoological Society of London exhibited specimens of 

 lepidopterous insects bred in the insect house of the Zoological 

 Society in London. Four cases containing specimens of 

 imagines or perfect insects, raised from chrysalides or pupae in 

 the Zoological Society's insect-house in the season of 1892. 

 They belong chiefly to the silk-producing moths of the family 

 Bombycidae, and to the diurnal lepidoptera or butterflies. 



Remains of extinct birds from New Zealand and the Chatham 

 Islands (oflf the coast of New Zealand), exhibited by Mr. H. O. 

 Forbes. The exhibit consisted of the chief portions of the 

 skeleton oi Aphanapteryx Hawkinst (Forbes), a genus of rails 

 known hitherto only from Mauritius, and of Palttocorax 

 Moriorum (Forbes), a large raven, a form not otherwise known 

 in the region ; portions of the skeleton of a ]&Tge J^u/ica, and of 

 a species of swan, now extinct, from the Chatham Islands ; a 

 part of the skull of a large Auserine bird allied to Ccrcopsis, 

 found associated with moa remains in a bog in New Zealand ; 

 the tibia of a new species of Cnemiornis, an extinct giant goose 



belonging to iron, 

 are also present. 



