May 25, 1905] 



NA TURE 



91 



Mechanical lantern slide illustrative of the phenomenon 

 of a total solar eclipse : Mr. W. Shackleton. A white 

 •disc representing the sun is projected on a screen ; by 

 moving an opaque disc representing the moon, this is 

 gradually obscured, and the preliminary partial phases of 

 a total solar eclipse are shown. A moment before com- 

 plete obscuration a twin shutter is opened, which allows 

 the corona and chromosphere to be projected, thus re- 

 producing totality, which may last as long as desired. — 

 Stereoscopic views of the sun and stars of estimated 

 parallax : Mr. T. E. Heath. The perspective drawings 

 were made from a plan and elevations in which the scale 

 of stellar distances was ten light-years to i inch, and of 

 stellar discs such that the sun (or a star which gives equal 

 light) was I /50th of an inch in diameter. The magni- 

 tudes were made to vary witli the varying distance of the 

 spectator. — (i) Microscope and goniometer stage for ex- 

 amining the optical qualities of minute grains of sand ; 

 (2) set of petrological quartz wedges ; (3) photomicro- 

 graphic camera, designed by Mr. J. W. Gordon for taking 

 small direct photomicrographs while the instrument is in 

 use after observation without attention to the adjustments : 

 Messrs. R. and J. Beck, Ltd. 



(i) Photomicrographs of section of gun tube showing 

 change in structure of steel after 2000 rounds ; (2) photo- 

 micrographs of alloys of aluminium with nickel ; (3) photo- 

 micrographs of alloy of copper with cobalt and nickel : 

 Dr. Hodgkinson, Captain Playfair, R.A., and Mr. Coote. 

 — (i) Apparatus for polishing and preparing metals for 

 microscopic examination ; (2) specimens of steels in the 

 cast and forged condition containing phosphorus : Mr. 

 J. E. Stead, F.R.S. — Transverse sections of slip-bands and 

 other microscopic features of metallic surfaces : Mr. W. 

 Rosenhain. — A series of alloys of iron and steel tested at 

 liquid air temperature : Mr. R. A. Hadfield. The speci- 

 mens showed the effect of liquid air (temperature 

 — 182° C.) upon almost pure iron (Swedish charcoal iron 

 " S.C.I.," 0-04 carbon, 99-82 iron) and a large number of 

 alloys of iron with other elements. The well known 

 ductility of iron disappears, while its tenacity is more 

 than doubled. Similar effects occur with nearly all the 

 alloys of iron with carbon and other elements, e.xcept those 

 containing nickel, which metal appears to modify con- 

 siderably the embrittling effect of low temperatures upon 

 iron. 



Clock and chronometer by Thomas Mudge : Mr. A. 

 Mallock, F.R.S. The clock was made about 1776, and 

 contains Mudge 's moon motion. Mudge's object in making 

 this motion was to show that any desired velocity ratio 

 could be approximated to very closely with comparatively 

 few wheels. The train of wheel-work he employed makes 

 the mean lunation 0-03 second less than the actual mean 

 lunation, that is, the error is less than i in 2^ millions. 

 There are other remarkable features in this clock con- 

 nected with the balance wheel, escapement, and tempera- 

 ture correction. — (i) Tangent-micrometer for theodolites, 

 &c. ; (2) endless-tangent screw for sextants : Mr. E. A. 

 Reeves. By the addition of a micrometer " drum," and a 

 simple arrangement for clamping the outer rim or dial 

 carrying the numbers, combined with a special indicator, 

 a carefully constructed tangent-screw serves also as a 

 micrometer, and renders it possible to read the arc with 

 the same accuracy as with the usual form of micrometer, 

 while the instrument need not be larger than the ordinary 

 vernier theodolite. The sextant device consists of a 

 tangent-screw constructed with an endless thread, by means 

 of which the vernier arm can be made to pass from any 

 one part of the arc to another. For making rough con- 

 tacts the tangent-screw is raised from the arc by means 

 of a lever pressed by the finger. When the pressure on 

 the lever is released the tangent-screw, actuated by a 

 spring, again comes in contact with the arc, and serves 

 as a clamp. 



A direct reading cymometer for measuring the 

 length of the waves used in wireless telegraphy : Prof. 

 J. A. Fleming, F.R.S. The instrument consists of a 

 sliding tubular condenser and an inductance coil, the 

 capacity and inductance being varied together in the same 

 proportion by one moveinent of a handle. The circuit is 

 closed by a copper bar, which is placed alongside the 

 aerial wire indicating the electric waves. The handle of 



NO. 1856, VOL. 72] 



the cymometer is then moved until a neon vacuum tube 

 used as an indicator shines most brightly, and thus de- 

 termines when the cymometer circuit is tuned to the 

 frequency of the aerial. A pointer moving over a scale 

 then indicates the wave-length of the radiated wave in 

 feet or metres. — An oscillation valve for rectifying electrical 

 oscillations and rendering them measurable on an ordinary 

 galvanometer : Prof. J. A. Fleming, F.R.S. The valve 

 consists of a bulb enclosing a carbon filament made like 

 an incandescence lamp. The filament is surrounded by 

 a metal cylinder. The bulb is highly e.xhausted. When 

 the filament is incandescent, negative electricity can move 

 through the vacuum from the hot filament to the cylinder, 

 but not in the reverse direction. Hence the arrangement 

 can separate out the two opposite currents in an electric 

 oscillation. It can be used in combination with a dead 

 beat galvanometer as a receiver in wireless telegraphy. 

 The valve replaces the coherer and other appliances, and 

 the signals are given by long and short deflections of the 

 galvanometer. — (i) Resonance induction coil and high 

 potential apparatus ; (2) resonance electromagnet : Messrs. 

 Isenthal and Co. Electrolytic condensers of very large 

 capacity are charged from the mains through the primary 

 of a suitably wound induction coil, and the circuit broken 

 and reversed at zero potential by means of a motor-driven 

 commutator of special construction. The advantages 

 are : — no motor transformer is required in primary circuit, 

 no rectifying device in secondary circuit, and there are 

 no interrupters to be cleaned. The apparatus enables a 

 current to be converted sparklessly into pure sine current 

 suitable for space telegraphy. An electromagnet excited 

 from a source of this kind exhibits peculiar physical and 

 physiological phenomena. — (i) High-tension resonance 

 transformer ; (2) X-ray stereoscope : Mr. Russell Wright. 

 The special form of " step-up " transformer exhibited 

 works direct from the alternating current mains, and pro- 

 duces an alternating discharge of sufficient tension for 

 X-ray work or high-frequency effluve. By means of a 

 small revolving shutter, driven by a synchronous motor, 

 between the observer's eye and two X-ray tubes, stereo- 

 scopic images could be clearly seen on an X-ray screen. 



High temperature electric furnaces : Director of the 

 National Physical Laboratory. These furnaces are con- 

 structed of rare earths such as are used in Nernst lamps. 

 They are available for temperatures between 800° C. and 

 2060" C. The apparatus used in a recent determination 

 of the melting point of platinum was shown at work, in 

 addition to that for other experiments of a similar 

 character. — New models of laboratory electric furnaces : 

 Mr. R. S. Hutton. The furnaces consist of a carbon tube, 

 rod, or plate heated by an electric current. In the tube 

 furnaces the carbon is surrounded by some material of 

 low thermal conductivity, which also serves to protect 

 the hot tube from oxidation. The substance to be heated 

 is placed in a carbon boat or crucible inside the tube, and 

 can thus be brought to a very high temperature. The 

 method employed for conveying the current to the carbon 

 by soldering water-jacketed sleeves to the electro-coppered 

 ends of the carbon forms a novel feature of the construc- 

 tion. 



Photographs taken in China by the Carnegie expedition 

 under Mr. Baily Willis in 1904, illustrating a presumably 

 Glacial deposit underlying the base of the Cambrian rocks 

 of the region : Sir Archibald Geikie, Sec.R.S. — Photo- 

 graphs, cast, and model of skull of Diplodocus, a Jurassic 

 dinosaur from Wyoming, and other fossils from the middle 

 west of North America : Dr. W. J. Holland. — Remains of 

 fossil mammals from Crete : Miss D. M. A. Bate. 

 Numerous mammalian remains were found in 1904 in the 

 Pleistocene cave and fresh-water deposits of Crete. These 

 include remains of the following animals : — antelope, deer, 

 elephant, pigmy hippopotamus, shrew, and two species of 

 rodents. — The great Indian earthquake, April 4 : Prof. J. 

 Milne, F.R.S. Five seismograms of this disturbance were 

 shown from Shide, Isle of Wight. (1-2) Open diagrams 

 on smoked paper showing north-south and east-west 

 motion. (3) Open diagrams of east-west motion on photo- 

 graphic paper. The instrument was a Milne horizontal 

 pendulum. (4-5) Photographic records from a pair of 

 Milne horizontal pendulums vibrated north-south and east- 

 west. The exhibit also included seismograms of east-west 



