July 9, 1896] 



XATCRI^ 



239 



reversed, so that the kathode was next the magnet, the excitation 

 of the maj^nel reduced the resistance of ihe tulie as formerly, the 

 green fluorescence al the same time disappearing ; but the blue 

 luminescence, instead of being concentrated into a cone, was 

 diffused throughout Ihe whole interior of the tube. 



[Since the aliove paper was written, further experiments have 

 revealed the following additional facts. 



With a tube of the form shown, exhausted to an extent that 

 gave X-rays plentifully under ordinary conditions, and supported 

 over an electro-magnet as .shown in Kig. i, the X-rays dis- 

 appeared as soon as the magnet was excited, but reappeared 

 the moment the magnet was demagnetised. 



With another lube of similar form but furnished with an 

 inclined platinum plate forming the anode placed near the 

 bottom of the tube, similar results were obtained. This tube 

 being kept on the pump was further exhausted to a degree that 

 allowed the electric discharge to pass with difficulty when the 

 magnet was not excited, and under these conditions gave X-rays 

 of a char.icter that penetrated the bones of the hand almost as 

 easily a< the flesh with but little contrast. With this exhaustion 

 Ihe excitation of the magnet not only caused the kathode rays to 

 focus on the platinum, thus giving sharper shadows, but at the 

 same time h.id piecisely the same eft'ect as lowering the vacuum 

 in so far as the moment the magnet was excited the X-rays 

 became more plentiful, and became of such a character as to 

 penetrate the flesh with much greater ease than the bone, so that 

 the c<mtrast between bone and flesh was exceedingly marked. 

 A photograph of the hand taken with one minute's exposure with 

 the tube in this condition, and with the magnet excited, though 

 considerably over-exposed, proved to be a very good one. 

 Further investigations are in progress, but the application of a 

 strong magnetic field in the manner described, gives promise of 

 having considerable practical utility, not only in so far as it 

 facilitates the accurate focusing of the rays proceeding from a 

 flat kathode upon any desired point of the platinum anode, but 

 also and more especially because by employing a high exhaustion 

 and by varying the intensity of the magnetic field, it is possible 

 at will to arrive with ease at the exact conditions requisite to 

 produce a maximum of X-rays of exactly the penetrative 

 character that may be best for any given purpose, a result which 

 hitherto has been difficult of attainment. — A. A. C. S. , July 7.] 



June iS. — "A Magnetic Detector of Electrical Waves, 

 and simie of its applications." By E. Rutherford, 1851 

 Exhibition Science Scholar, New Zealand University, Trinity 

 College, Cambridge. 



The cflect of Leyden jar discharges on the magnetisation of 

 steel needles is investigated, and it is shown that the partial 

 demagnetisation of strongly magnetised steel needles offers a 

 simple and convenient means for detecting and comparing 

 currents of great rapidity of alternation. 



The partial demagnetisation of a collection of fine steel wires, 

 insulated from each other, and over which is wound a small 

 solenoid in series with the receiving wires, was found to be a 

 sensitive means of detecting electrical waves at long distances 

 from the vibrator. A small but quite marked eft'ect was obtained 

 at a distance of half a mile from the vibrator. 



A fine steel wire detector was found to be of the same order of 

 sensitiveness as a bolometer for investigating waves along wires. 



This detector has the property of distinguishing between the 

 first and second half oscillations of a Leyden jar discharge, and 

 may be readily used for determining the damping of oscillations. 

 The absorption of energy of spark gaps of different lengths is 

 investigated. 



The resistances of iron wires for high frequency discharges 

 are quantitatively determined. The permeability of the different 

 specimens is deduced, and it is shown that the calculated value 

 of the iiermeability varies greatly with the diameter of the wire 

 and the intensity of the discharge. 



A method of experimentally determining the period of oscilla- 

 tion of a discharge is based on the division of a rapidly alternating 

 current in a multiple circuit, one arm of which is composed of a 

 standard inductance, and the other of a variable electrolytic 

 resistance. 



P.^RIS. 



Academy of Sciences, June 29. — M. A. Cornu in the chair. 

 — Some properties of the .secondary roots of prime numbers, by 

 M. de jonquicres. — Eonr.uUe for the coefficient of internal 

 friction in gradually varied flow of liquids, by M. J. Boussinesq. 

 — Remarks by M. Appell on presentation of his work on " The 

 principles of the theory of elliptic functions and their applica- 



NO. 1 393, VOL. 54J 



tions." — M. Albert Goudny announced the death of .Sir Joseph 

 I'restwich, correspondent of the Academy in the Sectipn of 

 Mineralogy. — ^L Bakhuyzen w-as elected a correspondent for the 

 Sf ction of Astronomy. — Report on a memoir of M. Ba/.in, entitled 

 " New experiments on the distribution of velocities in pipes." — 

 Control of the results obtained by the dynamometric pedal of 

 the bicycle, by ^L Bouny. Experiments in which the work 

 done was measured at the same time on the brake and by the 

 dynamometric pedal, .sh.iwed that about 95 per cent, of the 

 work exerted on the pedals was shown by the brake, the 

 remaining 5 per cent, being absorbed by the friction of the 

 axes of the pedals, the chain, and the axis joining the cranks. — 

 Actinometric experiments made on Mont Blanc with a view to 

 determine the solar constant, by M. J. Vallot. Simultaneous 

 observations were made at Chamounix and at the summit of 

 Mont Blanc. Two types of instrument were used, the absolute 

 actinometer of M. Violle, and the mercury actinometer of M. 

 Crova. Extremely concordant results were obtained, giving as 

 a mean value 170 for the solar constant. — On rays when A = o. 

 by M. C. Maltezos. — On the spectrum of phosphorus in fused 

 .salts and in certain metallurgical products, by M A. de (Sramont. 

 Fused jihosphates submitted to the action of a condensed spark, 

 give a fine spectrum of the lines of phosphorus of greater clear- 

 ness and intensity than the spectrum given by a PUicker tube 

 containing phosphorus. The same method showed easily the 

 presence of phosphorus in alloys, as little as 2 per cent, being 

 readily recognised by the characteristic triplet in the red. — On 

 the blue nitrodisulphonic acid and some of its salts, by \L Paul 

 Sabatier. — Action of iodine upon stannous chloride, by M. V. 

 Thomas. Mixed addition products, similar to those obtained 

 with bromine, were not found, the reaction taking a different 

 direction according to the equation 



3SnCl., -t- 7L = 3SnIj -1- 2ICI.,. 

 Thermal researches on the uranium compounds, by M. J. Aloy. 

 The heats of solution and formation of some of the commoner 

 uranyl .salts. — New method for the preparation of aromatic alde- 

 hydes, by M. L. Bouveault. The hydrocarbons are converted into 

 glyoxylic acids by means of ethoxalyl chloride in presence of 

 aluniinium chloride, and these heated with aniline give nearly 

 quantitative yields of phenylimides, the condensation to the pheny- 

 limido-acid and elimination of CO.j from the latter proceeding 

 simultaneously. A good yield of the corresponding aldehyde is 

 obtained on hydrolysing the phenylimide by boiling with dilute 

 sulphuric acid. The aldehyde group has in this way been in- 

 troduced into toluenes m-xylene, cymene, anisol, di-methyl 

 ether of resorcinol, and of di-methyl-hydroquinol. — Researches 

 on the chlorination of gallic acid. Formation of dichlorogallic 

 acid and of trichloropyrogallol, by M. A. Bietrix. — Crystallo- 

 graphic properties of benzylidene, methylsalicidene, ethylsali- 

 cidene, and anisol camphors, by M. J. Minguin. — On isaric 

 acid, a new unsaturated fatty acid, by M. A. Hebert. — Digestive 

 apparatus of Brachytrypes iiicinbraiiaceous, by M. Bordas. 

 This has many points of resemblance with the Gryllotalpa, but 

 differs from this species by the atrophy of the resophagus, 

 the reduction of the intestinal appendices, and especially by 

 the great length and numerous circumvolutions of the intes- 

 tine proper. — On a coloration of hepatic origin in the 

 oyster, by M. J. Chatin. — Petrographical study of the 

 meteoric stone that fell at Madrid. February 10, 1S96, 

 by M. Gredilla y Gauna. In the metallic portion schreibersite, 

 ivoilite, and chromite were recognisable, whilst the stony portion 

 contained the minerals peridote, enstatite, augite, plagioclase- 

 oligoclase felspar, and olivine. — The grotto of Spelugues, by 

 M. E. Riviere. This cave was discovered during the construc- 

 tion of a railway near Monte-Carlo, and contained human bones, 

 apparently from nine individuals. Other bones represented the 

 remains of animals resembling fox, hare, and sheep. The con- 

 clusion is drawn that the race of men represented by these 

 remains lived in the Neolithic period, and are quite distinct 

 from the race whose remains have been found in the cave of 

 Mentone. — On an electric variation determined in the acoustic 

 nerve when excited by sound, by MM. H. Beauregard and E. 

 Dupuy. — Action of diverse substances upon the movements of 

 the stomach, and the ennervation of that organ, by M. F. Bat- 

 telli. Of all the substances examined, muscarine, pilocarpine, 

 and physostigmine exercised the most energetic eft'ect upon the 

 movements of the stomach. Less energetic are nicotine and 

 other alkaloids, alcohol, and peptone ; whilst purgatives, strych- 

 nine, and pepsine were without action. — On specific heats, by 

 M. J. Taupin. 



