May 14, 1896] 



NA TURE 



2>7 



W. Friese (Jreene, turned oiu prints at a rate almost Ijeyond 

 belief. The machines are for the production of prints wholly or 

 partly by photography, and their chief object is to effect a very 

 rapid production of copies adapted for use as illustrated supple- 

 ments, newspapers or magazines, or for other purposes where a 

 large number of copies of the same picture, design, or other 

 objects are required. A roll of rapid bromide paper was fed in at 

 one end of each machine, and finished prints were turned out at 

 the other end at the rate of two or three thousand an hour. Mr. 

 Greene also showed a new type-setting machine dispensing with 

 movable types. 



Instantaneous photographs of splashes were shown by Prof. 

 Worthington, F.K.S., and Mr. R. S. Cole. These photographs 

 were taken each with an electric spark giving an exposure of 

 less than 3 millionths of a second (see N.\ture, vol. 1. p. 222.) 

 The spark could be so timed as to pick out any desired 

 stage of the splash within limits of error not exceeding, as a 

 rule, about 2-thousandths of a second. In this way the progress 

 of a great variety of splashes has been foUow'ed in minute detail. 

 .Specially interesting were those which illustrated the formation 

 of a bubble, and those which showed how the nature of the dis- 

 turbance produced by the entry of a solid sphere depended on 

 the condition of its surface. 



By means of the colour patch apparatus exhibited by Captain 

 Abney, C. B. , F. R. S. , it becomes possible to throw on a screen, 

 or on a photograi>hic plate, the image of a luminous object in 

 monochromatic light. An image is first formed on the face of a 

 prism or grating by means of a lens of proper focal length, placed 

 close to the slit of the spectroscope. The spectrum is formed 

 in the usual way, and the colour in which the image of the 

 object is to be formed is allowed to pass through a slit placed in 

 the spectrum. A second lens placed close to this slit forms the 

 image in monochromatic light of the image on the prism or 

 grating on a screen or photographic plate. 



Prof. Roberts-Austen, C.B., F. R..S., showed his interesting 

 modifications of an experiment of M. Charles Margot. A wire 

 of aluminium was raised, by a current of 30 amperes, to a 

 temperature far above the melting point of aluminium, but a 

 film of oxide on its surface prevented the wire from breaking. 

 The molten wire through which a current was passing, could 

 then be attracted by a magnet. 



On behalf of Mr. Carl Zeiss, new portable binocular field- 

 glasses and stereo-telescopes were exhibited. The objects of 

 the new types are (i) to obtain a considerably larger field than 

 that possessed by a Galilean telescope of similar magnifying 

 pow-er ; (2) to enhance the stereoscopic effect of the images 

 formed, by placing the object-glasses further apart than the eye- 

 pieces. These objects were attained by prisms and astronomical 

 oculars. The rays passing from the object-glass to the eyepiece 

 undergo four reflections at the surfaces of the prisms, and emerge 

 from the last prism with undiminished intensity. The inter- 

 position of the prisms serves to erect the inverted image formed 

 Ij}- the object-glass, and, at the same time, to displace the axis 

 of the eyepiece with respect to that of the object-glass, the 

 amount of this displacement being variable within wide limits. 



Mr. F. E. Ives had on view his stereoscopic photo-chromo- 

 scope. The photo-chromoscope camera makes, at a single 

 exposure on a commercial photographic sensitive plate, three 

 pairs of images, which by differences in their light and shade 

 constitute a record of everything that excites vision in the two 

 eyes. The stereoscopic photo-chromoscope translates this record 

 to the eyes, so that the object photographed appears to be seen 

 through it. 



The composite archer'.s bow, its structure and affinities, was 

 the .subject of an exhibit by Mr. Henry K.ilfour. Archers' bows 

 of composite construction, of wood or horn, or both, overlaid 

 with a "backing" or reinforcement of animal sinews, were 

 shown. There were com])lete bows from North-west America, 

 Japan, Corea, Manchuria, China, North India, &c., a composite 

 cross-bow from Germany, and an unique siiecimen of composite 

 bow from a tomb of the twenty-sixth d\ri.isty, Thebes, Egypt. 

 A map and diagram showing the ilistrilnuion and affinities of 

 the various types of composite bows were also exhibited. 



A bifilar pendulum in action was exhibit cd by the Cambridge 

 Scientific Instrument Company. This instrument w.as designed 

 by -Mr. Horace Darwin for observing and recording slow tilts 

 and pulsations of the earth's crust, by whatever cause they may 

 be produced, and is a modification of that used by the Messrs. 

 Darwin in 1881, at the suggestion of l.nrd Kelvin. It is 

 pos.sible to observe with this pendulum a till of less than ;jj,; of 



NO. T3.S5, vor. 54] 



a second, an angle less than that subtended by a line an inch 

 long placed at a distance of a thousand miles, as was shown by 

 the experiments made at Birmingham by Dr. Charles Davison. 



The results of experiments on steel gas cylinders were shown 

 by the Gas Cylinder Committee, lately nominated at the request 

 of the Home Office. These showed (l) the danger of using 

 hard orunannealed steel for gas cylinders ; (2) the extraordinary 

 amount of violent ill-treatment to which a good soft annealed 

 cylinder may be subjected without destruction, even when 

 charged to 120 atmospheres ; (3) the effect of very great internal 

 pressure steadily applied, in this case due to the expansion of 

 liquefied ammonia gas which completely filled the cylinder 

 when cold ; (4) the violently destructive character of the ex- 

 plosion of mixed gases under pressure which no practicable 

 cylinder can withstand. 



Portable apparatus for gas-testing in electric culverts was shown 

 by Prof. Clowes. A standard hydrogen flame, fed from a small 

 steel cylinder of the compressed gas, is enclosed in a brass vessel 

 provided with a transparent front. This apparatus is mounted 

 on a camera tripod, and is observed by throwing a black cloth 

 over the head. The air to be tested for inflammable gas is 

 pumped over the flame by dropping the end of a flexible tube 

 into the ctdvert, and compressing a rubber ball provided with 

 suitable valves. A constant stream of the air is thus caused to 

 pass over the hydrogen flame, and by the appearance and dimen- 

 sions of the flame-cap produced, gas is detected and its per- 

 centage is accurately measured. The hydrogen flame can be 

 adjusted to two standard heights, and thus percentages of gas 

 from 0'2 to 5 can be detected and measured. 



Geometric wall brackets were exhibited by the Rev. F. J. 

 Smith. F.R.S., and Prof. C. V. Boys, F.R.S. The brackets 

 have been designed with the object of providing wall supports 

 with definite position for physical apparatus. After the ap- 

 paratus and bracket have been adjusted, they may be removed, 

 and at any time immediately restored to their original position. 

 Tliis is found to be convenient where a class or lecture room is 

 used for some portion of a day only for physical demonstration. 

 The construction is as follows : — Three small projections, A, B, 

 C, are fixed to the wall, one of the two upper projections is 

 furnished with a three-sided indentation, the other with a V- 

 groove, the third is a flat surface ; two hemispherically ended 

 screws drop into the upper projections, and the third screw at 

 the bottom of the bracket rests against the flat surface. 



Geoiiietric steady blocks were also exhibited. These have been 

 designed so as to rest each on the one below it, upon six inde- 

 pendent small surfaces, so as to be geometrically clamped. 

 Thus any number of blocks may be piled to the desired height, 

 and carry physical apparatus with perfect steadiness. Both 

 square and triangular forms were shown. 



M. Maurice d'Ocagne, Professor at the ll^cole des Ponts et 

 Chaussees, exhibited a very complete series of " abaques " of his 

 invention, intended to perform certain calculations, such as the 

 solution of a cubic equation, or of Kepler's equation, and 

 generally of any equation involving three or four variables. 

 The interest was purely mathematical, appealing to a select 

 few ; but the applications of the principle are numerous and 

 important. , 



Mr. W. Barlow exhibited models to show the nature of the 

 repetition in space which characterises a homogeneous structure 

 having cubic symmetry. 



Specimens of ancient "astrolabes" and other instruments 

 were exhibited by Mr. Lewis Evans. 



Messrs. Read, Campbell, and Co. showed "aerators" for 

 aerating water and other liquids. The aerator is used in com^ 

 bination with a soda-water bottle and patent stopper. It is 

 made of sheet steel, and contains compressed carbonic acid gas ; 

 the soda-water bottle being filled with water or other liquid, the 

 aerator is inserted in the stopper, and the closing of the latter 

 liberates the gas, producing strongly aerated water or other 

 licpiid. The aerators may be charged with other gases and used 

 for other purposes than aerating liquids. 



There were exhibited by the Meteorological Council : (l) Cur- 

 rent charts of the Indian Ocean for the months of January, 

 April, July, and October. The currents shown on these charts 

 had been generalised from a very large number of observations, 

 the arrows and figures .ittached to them indicating the direction 

 and maximum and minimum velocities of the current likely to be 

 experienced at any particular spot. (2) Wind charts of the 

 .South Indian Ocean, between the Cape of Good Hope and New 

 Zealand, for the months of January, April, July, and October. 



