Bronze Strips Research Articles

Societies and Academies

LEEDS. Philosophical and Literary Society, June 19.—J. Ewles: A torsion magnetometer. A new instrument for laboratory use based on the principle that the couple required to hold a magnet of moment M at right angles to a field H is MH. Magnetic forces are removed by balancing against the torsion in a phosphor bronze strip supporting the ‘needle.’ All the experiments usually performed with both the deflection and vibration magnetometers may be performed with this instrument.—F. A. Long: Note on the behaviour of a neon-tube under heavy discharge. When using a neon (‘Osglim’) lamp in parallel with the coils of an electromagnet, the discharge through the lamp on breaking the current was of bright bluish-violet colour instead of the usual pink glow, and included two or more flashes. An examination of current voltage during the discharge shows that at the commencement a current of several amperes passes, while the voltage falls much lower than the usual extinction value.—C. W. Shoppee: On the possibility of ring-chain valency tautomerism and of a type of mobile-hydrogen tautomerism analogous to the Wagner-Meerwein re-arrangement. Part 5: Pina-colic electron displacement as an explanation of various intramolecular transformations. A discussion and an attempted correlation of various intramolecular transformations on the basis of tautomeric change. The general mechanism proposed gives a satisfactory explanation of many known changes, and where divergences occur between theory and fact, reinvestigation confirms the theoretical prediction.—L. R. Johnson and A. Wormall: Potassium thiocyan-ate and the diastatic action of saliva and plant-diastases. Potassium thiocyanate exerts an activating influence on the diastatic action of human saliva, and this effect is significant, even with concentrations of the salt which may be present in the saliva. The thiocyanate appears to accelerate the first stages only in the hydrolysis of starch, and the rate of formation of reducing sugars is not markedly increased. The stimulating effect of this salt on the germination of potatoes and barley is discussed in relation to its influence on diastatic action.—R. G. S. Hudson and F. W. Anderson: On the Lower Carboniferous corals. Hettonia fallax, gen. et sp. n. The genus Hettonia, a member of the Clisiophyllidse, is characterised by a solid central column built of an axial rod surrounded by tabular thickening. Hettonia fattax, the only species as yet described, is remarkable in that it possesses a distinct gerontic stage in which there is no cohrmella, and therefore simulates Can-inia. In addition, dedifferentiation is a common occurrence in this species. Certain new and un-described structures are recognised in the ephebic stage of the corallite, and are attributed to calicular gemination. The prototheca and part of the brephic structure are built while the young corallite is still attached to the parent individual, and remain there after separation of the young form.—Lorna I. Scott and Ada B. Whitworth: A structural peculiarity of the exodermis of the root of Pelargonium. In the root of Pelargonium the hypodermal cells develop a convex band of thickening, which runs round each cell on the radial and transverse walls. At maturity, the bands consist of lignified cellulose, with traces of silica, and show characteristic optical properties, which disappear on treatment with cellulose solvents. —W. Garstang and Margery I. Platt: On the asym-rmetry and closure of the endostyle in Gyclosalpa pinnata. The authors describe from sections the structure of the closed endostyle of Gyclosalpa pinnata. They confirm the absence of the left marginal band, and confirm it as due to the development of an interlocking mechanism by which the endostyle is firmly closed as a tube. The missing band, however, is present at both extremities with normal relations. The endostyle possesses a posterior growing point (cf. larval Amphioxus).

A Dynamic Study of Magnetostriction

In a recent paper by Professor G. W. Pierce1 are described various effects which occur when a magnetic rod has superimposed upon it an alternating axial magnetic field of a frequency in the neighborhood of the natural mechanical frequency of the rod. Rods under the influence of magnetostriction can be made to play a part somewhat analogous to quartz crystals under the influence of piezoelectricity. If a ferromagnetic rod or tube is clamped so that it lies along the axis of a coil, the combination becomes an electrical vibration instru ment, and may be treated in the same way that telephone receivers are treated by Kennelly and Pierce,2 or by Kennelly in his book on vibration instruments.3 The present paper describes the measure ment of the dynamic electrical characteristics of various magnetostric tive rods and tubes, also the magnitude of vibration and other measurements that could be made conveniently at the same time. Method of Measurement.?The motional resistance and reactance are measured by connecting the coil containing the rod into an alternating current bridge, as in the reference2 mentioned above. In this particular experiment, the bridge was designed to pass a direct current as well as the alternating current through the coil, thus it was possible to maintain a known field on the rod at any time. The coil is a long solenoid to insure a uniform magnetic field. The coil is 120 cm. long, has an inside diameter of two inches, and at its center developes a field of 32.5 gauss per ampere. The rods are all about 90 cm. long, and their natural frequencies lie between 2300 and 3000 cycles per second. In all measurements the superimposed alternating field is small compared to the direct or polarizing field. In measurement of amplitude of vibration, an extremely light phosphor bronze strip upon which is mounted a small mirror is fastened from the end of the rod to the stationary frame to which the center of the rod is clamped. The longitudinal vibration of the rod thus gives an angular motion of the mirror. A point source of light reflected from the mirror is observed in a telescope with a

An Electrostatic Oscillograph

The Paper describes an electrostatic oscillograph suitable for recording very high voltages. Two vertical bronze strips pass symmetrically between two parallel metallic plates called field plates. They are connected at their lower ends by a silk fibre which passes under an ivory pulley. An extremely small mirror is fixed to the strips. This arrangement constitutes the vibrator, which, mounted on an ebonite frame, is immersed in an oil bath. To the upper extremities of the strips are connected the terminals of a direct-current voltage of about 300. The alternating voltage to be recorded is connected to the field plates, in parallel with which there are two oil condensers in series. The electrical midpoint of the direct-current battery is connected to a point between the condensers. The turning moment on the strips is proportional to the product of the momentary values of the alternating-current voltage and the direct-current voltage, so that if the latter is constant, the deflection of the mirror accurately follows the variation of the former. Oil plays an important part, not only acting as a damping agent and insulator, but increasing the sensitiveness on account of its high dielectric constant. In cases where voltage is low, but the source of energy is so limited that a sufficient current cannot be taken to actuate the ordinary oscillograph, the electrostatic vibrator may be used by applying the voltage in question to the strips, while the terminals of a high-tension battery, or influence machine, are connected to the field plates. The instrument may also be used for recording very small currents by replacing the oil condensers by two exactly equal resistances, which are traversed by the current.

Societies and Academies

Societies and Academies