A SPARK-ADJUSTER FOR THE HOLTZ MACHINE.
In the Annalen der Physik und Chemie, Bd. cxxxvii. p. 452, and Bd. cxxxix. p. 509, under the title of "Schwache elektrische Funken in Luft, von P. Riess," a method is described of obtaining different kinds of electric sparks from the Holtz machine.
The following method seems to be preferable to that described in the above-mentioned articles:--Having insulated the outer coating of the two Leyden jars which form a part of the ordinary Holtz machine, short thick wires were connected with these outside coatings and terminated in two brass pointers or conductors, so arranged that the distance between them could be varied at pleasure. At first the conductors were placed in connexion with each other; it was then found that a series of sparks were given off between the conductors of the machine. The extreme length of spark obtainable with the machine which was used was 20 centims. The sparks so obtained were large and luminous, passing only at intervals, and requiring a certain electric tension before they would leap across the space. Then the pointers connected with the outer coatings of the Leyden jars were drawn apart about 13 millims. ; it was then found that a succession of fine thread-like sparks passed across the space separating the conductors of the machine, whereas there was no such appearance between the pointers connected with the jars. But at intervals a larger spark, not so bright as the normal spark of the machine, would jump across the conductors; and simultaneously with this a similar spark passed between the pointers. This fine line of sparks was found to have a peculiar form, being brightest and largest at the ends of the conductors of the machine, fading away to a lighter and redder tint, and being of a thread-like character in the space between the knobs of the conductors.
It was found, if the distance between the conductors of the machine exceeded a little that between the pointers connected with the Leyden jars, that no large sparks passed between either set of conductors, but only a series of thread-like discharges. When the distance between the conductors of the machine was less than that between the pointers, a similar result was obtained. When the pointers were but a few millimetres apart, a continuous loop-like discharge passed between them, which was not interrupted by the occasional passage of a bright spark, and was not coincident in path with the latter. By varying the distance of the pointers of the Leyden jars, the number and character of the sparks could be changed at will. This method possesses the advantage that by an easy adjustment of these pointers the form of the electric spark can be readily studied. In experimenting upon the passage of the spark through different media, we can by this method diminish the diameter, so to speak, of the spark, and can change quickly from the spark discharge to that of the brush. The change in tone of the sound of the discharge, when the distance between the pointers is varied, is quite marked.-Silliman's American Journal, May 1874.
ADHESION, on apparent, 465. Æther, on the number and weight of the molecules of, contained in electric conductors, 190.
Air, on the condensation of a mixture of, and steam on cold surfaces, 67; on the law of gyration of the, 229. Air-battery, on an, 61.
Alloys, on the electromotive and ther- moelectric forces of some metallic, in contact with copper, 28; on the quantitative analysis of certain, by means of the spectroscope, 311. Atmosphere, on the acoustic transpa- rency and opacity of the, 277, 374. Barometer, on a variation-, 362. Barrett (Prof. W. F.) on the molecu- lar changes that accompany the magnetization of iron, nickel, and cobalt, 51.
Books, new:-Wilson's Elementary Geometry, 56; Pierce's Practical Solid or Descriptive Geometry, 153; Yarnall's Catalogue of Stars, 155; Hawtrey's Elements of Euclid, 215; Tait's Quaternions, 364; Muir's Expression of a Quadratic Surd, 366; Proctor's Universe, 367; Reeks's Elementary Astro- nomy, 374.
Bourbouze (M.) on a process for ve- rifying the nodes in a sounding pipe, 80.
Bouty (E.) on the permanent mag- netism of steel, 315.
Brodie (Sir B. C.) on the electric de- composition of carbonic-acid gas, 309.
Bromide of silver, on the sensibility to light of, 273. Brough (R. S.) on Wheatstone's bridge, 22.
Broun (J. A.) on the period of hemi- spherical excess of sun-spots, 311.
Buchanan (J. Y.) on an apparatus for gas-analysis, 1.
Calendar, on a new form of, 357. Capillary and electrical phenomena, on the connexion between, 281. Carbonic-acid gas, on the electric de- composition of, 309.
Carpenter (Dr. W. B.) on the phy- sical cause of ocean-currents, 359.
Cayley (Prof.) on the mathematical theory of isomers, 444.
Cazin (A.) on the calorific effects of the magnetism in an electromagnet with several poles, 392. Challis (Prof.) on the source of ter- restrial magnetism, 14; on the analytical principles of hydrodyna- mics, 25; on the effects produced by fog and vapour on the intensity of sound, 277.
Chambers (F.) on the diurnal varia- tions of the wind and barometric pressure at Bombay, 228. Circle-quadrature, on Sylvester's and other forms of continued fraction for, 331.
Cobalt, on the molecular changes that accompany the magnetization of, 5]. Condensers, on telegraphic signalling with, 426.
Contact theory of the galvanic cell, on the new, 401.
Cooke (Prof. J. P.) on the Vermicu- lites, their crystallographic and chemical relations to the micas, and on the variation of the opti- cal angle in these minerals, 241. Croll (J.) on the physical cause of ocean-currents, 94, 168, 434. De la Rive (A.) on the effects of mag- netism on the electric discharge through a rarefied gas, 462.
Desains (P.) on Newton's coloured
rings, 236. Dewar (J.) on the physical constants of hydrogenium, 334. Diffraction-gratings, on the manufac- ture and theory of, 81, 193. Disk, on the heating of a, by rapid rotation in vacuo, 219.
Ebonite, on the expansibility of, by heat, 156.
Electric conductors, on the number and weight of the molecules of æther contained in electric conduc- tors, 190.
discharge, on the effects of mag- netism on the, through a rarefied gas, 462.
Electrical machines, on a simple con- densing collector for frictional, 49.
and capillary phenomena, on the connexion between, 281.
resistance, on the absolute value of the Siemens mercury unit of, 294, 342.
Electricity, on the action of, on gases, 309.
Electrified conductors, on the dis- charge of, 157.
Electrodes, on the disintegration of the, in the galvanic arc of light, 6. Electromagnet, on the calorific effects of the magnetism in an, with seve- ral poles, 392.
Electromagnetic unit, on the number of electrostatic units in the, 218. Elliptic transcendent identity, on the verification of an, 437. Energy, on the measure of work in the theory of, 291.
Fleming (J. A.) on the new contact theory of the galvanic cell, 401. Fluid, on double refraction in a vis- cous, in motion, 390.
Fog, on the effects produced by, in the atmosphere, on the intensity of sound, 277, 374.
Fraunhofer's lines, on the determina- tion of the prime angle of incidence and prime azimuth for the different, 321. Galvanic polarization in liquids free from gas, observations on, 145.
cell, on the new contact theory of the, 401. Gas-analysis, on an apparatus for, 1.
Hautefeuille (P.) on hydrogenized pal- ladium, 397.
Heat, on the mechanical equivalent of, 155; on the expansibility of ebonite by, 151. Heaviside (0.) on Wheatstone's bridge, 93; on telegraphic signal- ling with condensers, 426. Helmholtz (Dr.) on galvanic polariza- tion in liquids free from gas, 145; on the limits of the effective power of microscopes, 236. Herschel (Capt. J.) on a new form of calendar, 357.
Herwig (H.) on the disintegration of the electrodes in the galvanic arc of light, 6; on the number and weight of the molecules of æther contained in electric conductors, 190.
Hesse (Mr.) on the direct solution of a geometrical problem, 354. Holtz machine, on a spark-adjuster for the, 467.
Hübener (J.) on a peculiar oecurrence of crystallized silicic acid, 319. Hydrodynamies, on the analytical principles of, 25, 143.
Hydrogenium, on the physical con- stants of, 334.
Ice, on some crystalline forms of, 122.
Illumination, on some phenomena of, 77.
Insulated wires, on a method of find- ing faults in, 416.
Iron, on the molecular changes that accompany the magnetization of, 51. Isomers, on the mathematical theory of, 444.
Jefferisite, on the crystallographic structure and chemical composition of, 252.
Karstenite, on some crystalline forms of, 122.
Ketteler (Prof.) on the boundary-con- ditions of reflection and refraction for the principal section of media in motion, 411. Kohlrausch (F.) on the expansibility of ebonite by heat, 156; on the absolute value of the Siemens mer- cury unit of electrical resistance, 294, 342; on a variation-barome- ter, 362.
Lallemand (A.) on some phenomena of illumination, 77. Light, measurements of the polariza- tion of the, reflected by the sky and by one or more plates of glass, 127; on some phenomena of polarization by diffusion of, 205; on the action of, on the electrical resistance of selenium, 216; on extraordinary developments of, in grinding hard stones, 237; on the sensibility of bromide of silver to, 273; on the intensity of reflected and refracted, 411.
Lippmann (G.) on the connexion be-
tween capillary and electrical phe- nomena, 281.
Liquids, on galvanic polarization in, 145.
Lockyer (J. N.) on the quantitative
analysis of certain alloys by means of the spectroscope, 311; on spec- trum-analysis, 384.
Lohse (O). on the spectrum of the
light of exploding gun-cotton, 319. M'Kichan (D.) on the number of electrostatic units in the electro- magnetic unit, 218.
Mädler (Dr. J. H. von), notice of the late, 320.
Magnetic forces, on the theory of the, 318.
Magnetism, on the source of terres-
trial, 14; on the 26-day period of terrestrial, 311; on the calorific effects of the, in an electromagnet with several poles, 392: on the effects of, on the electric discharge through a rarefied gas, 462.
of steel, on the permanent, 315.
Maxwell (J. C.) on double refraction
in a viscous fluid in motion, 390. Metallic alloys, on the electromotive and thermoelectric forces of some, in contact with copper, 28. Micas, on the crystallographic and chemical relations of the vermicu- lites to the, 241. Microscopes, on the limits of the effective power of, 236.
Milky Way, on the constitution of the, 370.
Miller (Prof. W. H.) on quartz, ice, and Karstenite, 122.
Mines, on the composition of the waters from some, 164.
Minot (J. J.) on a spark-adjuster for the Holtz machine, 467.
Moon (R.) on the analytical princi- ples of hydrodynamics, 143; on the measure of work in the theory of energy, 291.
Moutier (J.) on the discharge of elec- trified conductors, 157. Muir (J.) on Sylvester's and other forms of continued fraction for circle-quadrature, 331.
Newton's coloured rings, experimen tal researches on, 236. Nickel, on the molecular changes tha accompany the magnetization o 51.
Nöggerath (Prof. J.) on extraordinar developments of light in grindin hard stones, 237.
Ocean, on the chemistry of the, 1. Ocean-currents, on the physical cau
of, 94, 168, 359, 434.
Oolites of Northamptonshire, on t 74.
Ozone, on the composition of t unit of, 310.
Palladium, on hydrogenized, 397. Phillips (J. A.) on the composit of certain mine waters, 164. Photography, improvements in, 2 Pickering (Prof. E. C.) on the po ization of the light reflected by sky, and by one or more plate glass, 127.
Polarization, on some phenomen by diffusion of light, 205. Quartz, on some crystalline form 122.
Quincke (G.) on the determinati the prime angle of incidence
prime azimuth for the different Fraunhofer's lines, 321. Rayleigh (Lord) on the manufacture and theory of diffraction-gratings, 81, 193; on the theory of resona- tors, 419.
Reflection and refraction, on the boundary-conditions of, for the principal section of media in mo- tion, 411.
Refraction, on double, in a viscous fluid in motion, 390. Resonators, on the theory of, 419. Reynolds (Prof. O.) on the conden- sation of a mixture of air and steam on cold surfaces, 67. Roberts (S.) on a simple condensing collector for frictional electrical ma- chines, 49.
Roberts (W. C.) on the quantitative analysis of certain alloys by means of the spectroscope, 311. Rosse (the Earl of) on the electric resistance of selenium, 161. Royal Institution, proceedings of the, 374.
Royal Society, proceedings of the, 61, 216, 309, 384, 447.
Sale (Lieut.) on the action of light on the electrical resistance of selenium, 216.
Sarasin (E.) on the effects of mag- netism on the electric discharge through a rarefied gas, 462. Secchi (Father A.) on the tempera- ture of the sun, 394. Selenium, on the electric resistance
of, 161; on the action of light on the electrical resistance of, 216. Serrano y Fatigati (H.) on the me- chanical equivalent of heat, 155. Sharp (S.) on the oolites of North- amptonshire, 74.
Siemens mercury unit of electrical resistance, on the absolute value of, 294, 342.
Silicic acid, on a peculiar occurrence of crystallized, 319.
Sky, measurements of the polarization
of the light reflected by the, 127. Soret (J. L.) on some phenomena of polarization by diffusion of light, 205.
Sound, on the effects produced by fog and vapour in the atmosphere on the intensity of, 277, 374.
Steam, on the condensation of a mix- ture of, and air on cold surfaces, 67.
Steel, on the permanent magnetism of, 315.
Stefan (J.) on the theory of the mag- netic forces, 381; on apparent ad- hesion, 465.
Sterlingite, on the crystallographic structure and chemical composition of, 247.
Stewart (Prof. B.) on the heating of a disk by rapid rotation in vacuo, 219.
Sun, on the spectrum of the, 384; on the temperature of the, 391. Sundell (Dr. A. F.) on the electro-
motive and thermoelectric forces of some metallic alloys in contact with copper, 28. Sun-spots, on the period of hemi- spherical excess of, 311.
Tait (Prof. P. G.) on the heating of a disk by rapid rotation in vacuo, 219. Telegraph-lines, on the testing of, 22, 93, 416, 426.
Terquem (A.) on the vibroscope tono- meter, 212.
Thomson (Prof. J.) on certain rela- tions between the gaseous, the liquid, and the solid states of water-substance, 447. Tonometer, on the transformation of the vibroscope into a, 212. Tribe (A.) on an air-battery, 61. Troost (L.) on hydrogenized palla- dium, 397.
Tyndall (Prof.) on the acoustic trans- parency and opacity of the atmo- sphere, 374.
Vapour, on the effects produced by, on the intensity of sound, 277, 374. Vermiculites, on the, their crystallo- graphic and chemical relations to the micas, 241.
Vibrations, on the determination of the absolute number of, 212.
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