i86 



NA TURE 



[June 25, 1896 



ihe largest prominences depicted in all the pholoj^raphs was not 

 seen at all at Kalocsa. The results with Ihe spectroheliograph 

 were not of the best, owing to haze ; but from all available 

 facts, it seems to be established that the white prominences are 

 spectroscopically invisible because they shine chiefly by H and K 

 light. Nevertheless, light of the same refrangibility in the 

 electric arc undoubtedly appears violet ; but it may be, as Prof. 

 Hale suggests, that the violet tinge is overlooked in the presence 

 of the more conspicuous colours during an eclipse. The best 

 results obtainable with the spectroheliograph, when K light is 

 utilised, compare very favourably in .sharpness of definition, as 

 well as in the rendering of faint details, with the best photo- 

 graphs taken during an eclipse. 



Shootint.-Star R.-\di..\nts. — In connection with a table of 

 radiant points observed at Hong Kong, Dr. Doberck refers to 

 several interesting points relating to the phenomena of shooting- 

 stars {Ast. Nadi. , 3360). It is pointed out that the long con- 

 tinuance of some of the radiants is accounted for by parabolic 

 motion, while others can possibly be explained by hyperbolic 

 motion. In explanation o( some of the radiants having some- 

 what similar elements, it is suggested that they were possibly 

 associated with different tails of the same comet. 



Owing to the fact that the meteorites are heated to incan- 

 descence nearer the earth in the evening than in the morning, 

 there is a small decrease in the average magnitude of shooting- 

 stars during the night; before 9 p.m. the average brightness is 

 mag. 27, while of those seen later it is 3 '2. Again, on account 

 of the earth's movement, the duration decreases from O'g sec. 

 between 6 and 8 p.m. to o'5 sec. between 8 and 11 p.m., and to 

 0'3 sec. between 11 p.m. and 4 a.m. Up to 11 p.m. the mean 

 length of path is 15°, and afterwards 13°. The average duration, 

 length, angular velocity per second, and the numbers of shooting- 

 stars observed, classified according to magnitude, are shown in 

 the following table : — 



iMag. Duration. Length. Velocity. Number. 



60 

 79 



4 03 12 40 128 



5 02 12 60 97 



The majority of the shooting-stars below third magnitude 

 were probably hidden by haze and artificial light. 



Kepler anp his Work. — In a little pamphlet entitled 

 "Kepler's Lehre von der Gravitation" (Halle, Max Niemeyer), 

 Dr. Ernst Goldbeck gives an interesting and appreciative 

 account of Kepler and his work. The point principally 

 elaborated is a main difference between Kepler's methods and 

 those pursued by Ptolemy and the older astronomers. These 

 latter were content to solve the problem of celestial mechanics 

 on purely mathematical lines. They were instructed in the 

 shape of the orbits and their dependence on time ; they could 

 foretell the place of an object at a definite epoch, and this satis- 

 fied their astronomical needs. Kepler, however, the forerunner 

 of the modern school, is concerned in the character and the 

 operation of the force, on which these motions depend. The 

 points surveyed by the author as affecting the development of 

 Kepler's views in his approach to a gravitational theory of the 

 earth are: (i) The transference of the centre of the solar 

 system from the earth to the sun, and the consequent disturbance 

 of Aristotle's views. (2) The impetus given to mechanical 

 inquiry by Gilbert's magnetical investigations. (3) The discovery 

 of the coincidence of tidal phenomena with the position of the 

 moon, and con.sequently the suggested attraction. (4) The 

 telescopic examination of the moon by Galileo, and the con- 

 firmation of the suspected identity of its general character with 

 that of the earth. Kepler's work on Mars, and his endeavours to 

 trace the nature of the connection between the sun and the 

 planets, are graphically described, and the whole pamphlet well 

 repays careful study. 



SCIENCE AND SOCIETY AT THE CENTRAL 



TECHNICAL COLLEGE. 

 'PHE object of the conversazione at the Central Technical 

 College, Exhibition Road, on Friday, June 12, was to 

 enable the scientific public to witness the ordinary working life 

 of the students there. Consequently, while in deference to the 

 lady visitors, the staircases and corridors were rendered attractive 



with arches of palms, armchairs, arc lights, and Hungarian airs, 

 neither the blossoms, the banners, nor the band, were allowed 

 to intrude on the apparatus and machinery, which were left as 

 in every-day use. 



Laboratory sinks remained sinks, and were not converted into 

 make-believe flower-boxes ; while no green baize covers hid 

 the traces of oil and tools on the workshop benches, nor made 

 them resemble extemporised billiard tables. 



The Lord Chancellor, as Chairman of Council, and Lady 

 Halsbury, received the visitors, and conspicuous amongst the 

 1700 were the .Masters of many of the City Companies wearing 

 their chains of oftice. 



Exactly twelve years ago to-day (June 25, 1896) the Central 

 Technical College was opened by the Prince of Wales, who 

 expressed the opinion, " that the opportunities for advanced 

 instruction, which will be afforded in the well-arranged labora- 

 tories and workshops, will enable the managers and superintend- 

 ents of our manufacturing works to obtain more readily than 

 hitherto the higher technical instruction which is so essential to 

 the development of our trade and commerce." And, on the same 

 occasion, the late Lord Selborne — the then Lord Chancellor — 

 stated that " in the several laboratories with which this College 

 is provided, new and increased facilities will be afl'orded for the 

 prosecution of original research, having for its object the more 

 thorough training of the students, and the elucidation of the 

 theory of industrial processes." 



An examination of the laboratories and work.shops by the 

 visitors at the conversazione, made it clear that the aim.s 

 initially laid down for the working ot the Central Technical 

 College have been .steadily kept in view. The Department of 

 Mechanics and Mathematics showed the apparatus which had 

 been developed for familiarising students with the laws of motion 

 and force. Electric clocks transmit time-signals to quick-running 

 Morse instruments for chronographically marking the instants of 

 various experimental events. To measure ".i' " the falling body 

 is started electrically, its moment of arrival noted electrically, 

 and the interval measured with a vibrating tuning-fork ; while 

 for slower motions, such as that of a body rolling down an in- 

 clined plane, the electric current that liberates the ball starts a 

 stream of water flowing from a water-clock, which again is 

 instantly stopped on the ball touching an electric trigger 

 placed at any desired point of its path. Apparatus for 

 measuring centrifugal forces, studying impact, finding moments 

 of inertia, timing the vibrations of pendulums, measuring the 

 extensions of wire, &c. , make us wish that, when, as boys thirty 

 or forty years ago, we laboured through " little Newth," ac- 

 quired a particle of Tait and Steele, and struggled with the 

 rigidity of Routh's Dynamics, some Maxwellian demon had 

 opened the door of Prof. Henrici's laboratory, and shown us so 

 vivid a realLsalion of the principles of what, in the misleading 

 jargon of that day, was called "statics and dynamics," with its 

 •'accelerating forces" and " moving forces." 



In the same department were seen calculating machines and 

 quadric surfaces, planimeters and plaster of Paris models, inte- 

 graphs for solving differential equations, and integrators for 

 evaluating areas : while the smooth working of the latest form of 

 Prof. Henrici's harmonic analyser, by means of which ten co- 

 efficients in a Fourier's series can be determined by going only 

 once over a curve, led the engineer to speculate on the time 

 when all calculations, however complex, would be done by 

 turning a handle, and when the brain would be left quite free to 

 think and originate. 



So much attention has of late been given by School Boards and 

 County Councils to the establishment of manual training classes, 

 that the collection of exercises in wood-working in the Carpenter's 

 Shop of the Engineering Department, could not fail to attract 

 attention. But more attractive still was the laboratory 

 for testing materials, where the deliberate motion of the 

 lever of the 100-ton machine, stretching steel plates until they 

 broke, and automatically writing the history of the experiment 

 with Prof. Unwin's stress-strain-recorder, was as fascinating to 

 the lady-visitors as to the engineers who accompanied them. 

 And how complete is the investigation that the students can 

 make on the properties of the materials used by the engineer and 

 builder, could be gathered from seeing the smaller machines 

 which were bending thick beams of wood, stretching wires, 

 and breaking blocks of cement, as well as from examining those 

 specially designed for testing lubricants, gauges, and the elastic 

 constants of materials, such as the screw and mirror extenso- 

 meters and compressometers designed by Prof. Unwin. 



NO. I 39 I, VOL. 54] 



