NATURE 



[July 28, 1910 



Welwitschia, Mrs. Thoday; further observations on 

 the fossil flower, Dr. M. C. Stopes; chromosome re- 

 duction in the Hymenomycetes, Harold Wager ; the 

 sexuality of Polystigma rubrum. Prof. V. H. Black- 

 man; telophases and prophases in Galtonia, Prof. 

 Farmer and iMiss Digby ; a cytological paper, Dr. 

 H. C. J. Fraser; the zoospores and trumpet-hyphae of 

 the Laniinariaceae, Dr. Lloyd Williams; plant dis- 

 tribution in the woods of north-east Kent, M. Wilson ; 

 the absorption of water by leguminous seeds, A. S. 

 Home. Papers are also expected by Prof. F. E. 

 Weiss and others. The semi-popular lecture will be 

 given this year by Prof. F. O. Bower; subject, sand 

 dunes and ^oli links. 



Section L (Educational Science). — The president 

 for the meeting is Principal H. A. Miers, and 

 his presidential address will be delivered on Thursday 

 morning, September i. It is intended to give up the 

 whole of Friday, September 2, to the subject of educa- 

 tional research, and the meeting will be a joint one 

 with the Anthropological Section. Prof. J. A. Green, 

 of Sheffield, the secretary of a committee which has 

 been investigating the mental and physical factors 

 involved in education, will present a report on the 

 present position of educational research at 

 home and abroad. Dr. Gray will also pre- 

 sent a report on behalf of a committee of the 

 Anthropological Section on methods of 

 observing and measuring mental characters. 

 It is hoped that Prof. Munsterberg, of Har- 

 vard, will open the discussion, which pro- 

 mises to be an important one. Dr. Lucy H. 

 Ernst, Prof. Lippmann, of Berlin, Dr. Kerr, 

 the principal medical officer of the London 

 Countv Council, and several members of his 

 staff, Prof. C. S. Myers, Dr. T. P. Nunn, 

 and Dr. Rivers, of Cambridge, amongst 

 others, have signified their intention to take 

 part, and reports will be presented, by the 

 investigators, of serial observations on school 

 children and others which have been con- 

 ducted in London, Liverpool, Sheffield, Wolver- 

 hampton, and elsewhere. On Monday morning, 

 September 5, Mr. J. G. Legge, Director of Education 

 in Liverpool, will open a discussion on handwork and 

 science in elementary schools. On Monday afternoon 

 there will be a joint discussion with the Chemistry 

 Section on the neglect of science in commerce and 

 industrv. Mr. R. Blair, the Education Officer of the 

 London Countv Council, will open the discussion, and 

 Prof. Bovey, Principal E. H. Griffiths, Sir William 

 Tilden, and others have promised to take part. On 

 Tuesday morning, September 6, the subject of open-air 

 studies in schools of normal type will be taken up. 

 There will be papers bv Mr. J. E. Feasev, of Sheffield, 

 Mr. G. G. Lewis, of Kentish Town, and Prof. Mark 

 R. Wright, of Newcastle-on-Tyne, will read a paper 

 on a training college under canvas. On Tuesday 

 afternoon a joint meeting will be held with the Physio- 

 logical Section for the discussion of voice production. 

 Dr. A. A. Grav, Mr. H. H. Hulbert, Principal Bur- 

 rell, of Isleworth, Prof. Wesley Mills, Mr. W. H. 

 Griffiths, and others, will contribute papers. 



THE ULTRA-RAPID KINEMATOGRAPH. 



A RECENT number of La Wa/ure (April 30) contains 

 a very interesting account of the latest work 

 of the Marey Institute. By means of the new instru- 

 ment, the ultra-rapid kinematograph invented by M. 

 Bull, sharp stereoscopic kinematograph views may be 

 obtained of such extremely rapid movements as, for 

 instance, the flight of a 'fly or the breaking of a soap 

 bubble. With the ordinary kinematograph the photo- 

 NO. 2126, VOL. 84] 



graphic film moves discontinuously, being arrested at 

 the moment of each exposure. VVhile this is simple 

 enough at moderate speeds, it would be quite impos- 

 sible where the exposures are at the rate of 2000 a 

 second, and the mean speed of the film 4000 cm. a 

 second. These are the figures that are necessary for 

 the study of insect flight, and these are attained in the 

 new instrument. With such a speed the movement 

 of the film must be continuous, and a sharp image is 

 possible only if the exposure does not e.xceed 1/400,000 

 second, and for this the electric spark gives a light of 

 sufficiently short duration. 



The apparatus is shown diagrammatically in the 

 figure. R is a wheel 34'5 centimetres in diameter, 

 which may be turned at a high speed by means of an 

 electric motor. It carries two long strips of photo- 

 graphic film to receive the stereoscopic images. On the 

 same axis, but outside the octagonal light-proof case, is 

 fastened an interrupter, I, of fiftv-four strips of copper, 

 which serve to make and break the primary circuit of 

 an induction coil fifty-four times everv turn, or 2000 

 times a second. The secondary of the induction coil is 

 connected with a pair of spark-gaps, E. arranged in 

 series, the electrodes being of magnesium to increase 



the light. The arrangement of the two gaps and 

 their relation to the optical system are shown in plan 

 (but reversed, left for right) in the upper left-hand 

 corner of the figure. A condenser, L, is connected to 

 the wires leading to the spark-gaps. The optical 

 svstem is made clear by the figure, but the lenses are 

 made of quartz and Iceland spar instead of glass, so 

 as to be transparent to the actinic rays of short wave- 

 length for which glass is opaque. A mirror, M, throws 

 the pair of images on a ground-glass screen, D, or, on 

 being turned up out of the way, it leaves a clear 

 passage for them to be formed on the films. In order 

 to prevent the photographs from being spoilt by 

 multiple exposure, two shutters of thin steel, actuated 

 by springs, are released electromagnetically one after 

 the other, the interval being the duration of one turn 

 of the wheel. 



The movements photographed are determined as to 

 time by fine wire prolongations of the prongs of a 

 tuning-fork of 50 ~ a second, which are photographed 

 at each successive exposure, and as to distance by a 

 divided glass scale, which equally appears in every 

 picture. It is, of course, necessarv to ensure that the 

 fly or other insect shall traverse the field of view just 

 at the time that exposure is made. There is no diffi- 

 culty in causing the creature to flv in the right 

 direction, as a window is suflicient to determine the 

 line of flight. One method by which M. Bull releases 

 the fly at the right moment is by holdinp' it in electro- 

 magnetically-operated forceps, which are relaxed by 

 the same current which starts the first shutter. This 

 works well enough with ordinary flies, but hymen- 

 optera and some other insects hesitate and only make 



