scholarly journals On the magnetic power of soft iron

1837 ◽  
Vol 3 ◽  
pp. 187-188
Keyword(s):  
Electric Current ◽  
Copper Wire ◽  
Complete Removal ◽  
The Other ◽  
Present Communication ◽  
Hard Steel ◽  
Electric Current Passing ◽  
Good Contact ◽  
The One ◽  
Single Helix

When free magnetism is developed by induction, and is not retained in that state by what has been termed the coercive force of hard steel, it has generally been considered that all the phenomena due to the existence of free magnetism cease on the removal of the inducing cause. The object of the present communication is to show that such is not the fact. From a variety of experiments described by the author, it appears that soft iron continued to exhibit strongly the attraction due to the developement of magnetism long after the means by which the magnetism had been originally excited had ceased to act. In these experiments, bars of soft iron, in the form of a horseshoe, had a single helix of copper wire wound round them, so that on the ends of the wire being brought into contact with the poles of a voltaic battery, the iron became an electromagnet. With one of these horse-shoes, while the connexion between the ends of the helix and the poles of the battery existed, the soft iron, having a keeper applied to its poles, supported 125 pounds it supported 56 pounds after that connexion had been broken, and continued to retain the power of supporting the same weight after an interval of several days, care having been taken not to disturb, during the time, the contact between the horse-shoe and its keeper. On this contact, however, being broken, nearly the whole attractive power appeared to be immediately lost. The author describes several instances of the same kind, particularly one in which the contact between the ends of the horse-shoe of soft iron and its keeper having been undisturbed during fifteen weeks, the attractive power continued undiminished. Although the interposition of a substance, such as mica or paper, between the ends of the horse-shoe and its keeper necessarily diminished the force of attraction, it did not appear to diminish the power of retaining that force. In a case where the electromagnet of soft iron and its keeper were equal semi-circles, the author found, what may appear singular, that the arrangement of the magnetism during the time that the electric current traversed the helix, appeared not to be the same as after the cessation of that current; in the one case similar, and in the other dissimilar, poles being opposed to each other at the opposite extremities of the two semi-circles. Whether the magnetism was originally developed in the soft iron by means of an electric current passing round it, or by passing over its surface the poles of an electromagnet, or those of a common magnet of hard steel, it appeared to possess the same power of retaining a large portion of the magnetism thus developed. The retention of the magnetism does not appear to depend upon the relative positions of the ends of the horse-shoe and the keeper remaining undisturbed, but on their contact remaining unbroken: for one keeper was substituted for another without diminution of this power; care being taken that the second should be in good contact with both ends of the horse-shoe before the complete removal of the first.

scholarly journals Experimental researches in electricity

1837 ◽  
Vol 3 ◽  
pp. 91-93
Keyword(s):  
Electric Current ◽  
Copper Wire ◽  
The Other ◽  
Great Length ◽  
Electrical Currents ◽  
Electric Current Passing ◽  
Electrical Condition ◽  
The Moment ◽  
Electrical Induction ◽  
Experimental Researches

This paper is divided into four parts: the first being on the Induction of Electric Currents; the second, on the Evolution of Electricity from Magnetism; the third, on a new Electrical Condition of Matter; and the fourth, on Arago’s Magnetic Phænomena. The author defines electrical induction to be the power which electrical currents possess of inducing any particular state upon matter in their immediate neighbourhood. A great length of copper wire, 1-20th of an inch in diameter, was wound round a cylinder of wood so as to compose two helices, the coils of which were intermixed, but prevented from touching each other by interposed threads of twine and calico. One helix was connected with a voltaic battery, and the other with a galvanometer. No effect was perceived on the latter, with a battery of 10 plates; a slight effect only with one of 100 plates; and a distinct deflection of the needle of the galvanometer occurred when the contact was made with a battery of 120 plates. While the contact was preserved, the needle returned to its natural position, and was unaffected by the electric current passing through the wire connected with the battery; but on breaking the connexion, the needle of the galvanometer was again deflected, but in a direction contrary to that of its former deflection. Hence it is inferred that the electric current sent by the battery through one wire, induced a similar current through the other wire, but only at the moment the contact was made; and a current in the contrary direction when the passage of the electricity was suddenly interrupted. These transitory currents, resembling waves, were found to be capable of magnetizing needles placed within the helix. Collateral currents, either in the same or in opposite directions, exert no permanent inductive power on each other.

scholarly journals XXIII.—On the Disruptive Discharge of Electricity: An Experimental Thesis for the Degree of Doctor of Science, Department A

1878 ◽  
Vol 28 (2) ◽  
pp. 633-671 ◽  
Author(s):  
Alexander Macfarlane
Keyword(s):  
Copper Wire ◽  
Late Summer ◽  
The Other ◽  
Straight Line ◽  
Summer Session ◽  
The Difference ◽  
A Chain ◽  
The One ◽  
Metallic Parts ◽  
The University

The experiments to which I shall refer were carried out in the physical laboratory of the University during the late summer session. I was ably assisted in conducting the experiments by three students of the laboratory,—Messrs H. A. Salvesen, G. M. Connor, and D. E. Stewart. The method which was used of measuring the difference of potential required to produce a disruptive discharge of electricity under given conditions, is that described in a paper communicated to the Royal Society of Edinburgh in 1876 in the names of Mr J. A. Paton, M. A., and myself, and was suggested to me by Professor Tait as a means of attacking the experimental problems mentioned below.The above sketch which I took of the apparatus in situ may facilitate tha description of the method. The receiver of an air-pump, having a rod capable of being moved air-tight up and down through the neck, was attached to one of the conductors of a Holtz machine in such a manner that the conductor of the machine and the rod formed one conducting system. Projecting from the bottom of the receiver was a short metallic rod, forming one conductor with the metallic parts of the air-pump, and by means of a chain with the uninsulated conductor of the Holtz machine. Brass balls and discs of various sizes were made to order, capable of being screwed on to the ends of the rods. On the table, and at a distance of about six feet from the receiver, was a stand supporting two insulated brass balls, the one fixed, the other having one degree of freedom, viz., of moving in a straight line in the plane of the table. The fixed insulated ball A was made one conductor with the insulated conductor of the Holtz and the rod of the receiver, by means of a copper wire insulated with gutta percha, having one end stuck firmly into a hole in the collar of the receiver, and having the other fitted in between the glass stem and the hollow in the ball, by which it fitted on to the stem tightly. A thin wire similarly fitted in between the ball B and its insulating stem connected the ball with the insulated half ring of a divided ring reflecting electrometer.

The Paragenesis of Kyanite-amphibolites (With Plate XX.)

1937 ◽  
Vol 24 (158) ◽  
pp. 555-568 ◽  
Author(s):  
C. E. Tilley ◽  
H. C. G. Vincent
Keyword(s):  
The Other ◽  
Retrograde Metamorphism ◽  
Present Communication ◽  
The South ◽  
South Side ◽  
The Alps ◽  
The One

In an earlier paper the writer has discussed the paragenesis - kyanite-omphacite as observed in certain ec|ogites. The fate of this association under conditions of retrograde metamorphism has led to a consideration of rocks showing the paragenesis amphibole-kyanite, a point which is briefly taken up in the present communication. Rocks containing this latter assemblage include two groups, the one better known, of sedimentary origin, the other essentially igneous in origin.Here are included members of the para-amphibolites, biotite-hornblende- schists, and hornblende-Garbenschiefer derived from sediments of the character of calcareous and dolomitic shales. The best-known examples come from the Alps—particularly the Triassic and pre- Triassic sediments on the south side of the St. Gotthard massif.

scholarly journals IV. On the development of electric currents by magnetism and heat

1869 ◽  
Vol 17 ◽  
pp. 265-267
Keyword(s):  
Copper Wire ◽  
Glass Tube ◽  
Rubber Band ◽  
The Other ◽  
Internal Diameter ◽  
External Diameter ◽  
Thin Glass ◽  
Iron Wire ◽  
It Flexibility ◽  
Electric Current Passing

I have devised the following apparatus for demonstrating a relation of current electricity to magnetism and heat. A A, fig. 3, is a wooden base, upon which is supported, by four brass clamps, two, B, B, on each side, a coil of wire, C; the coil is 6 inches long, 1½ inch external diameter, and ⅜ of an inch internal diameter, lined with a thin glass tube; it consists of 18 layers, or about 3000 turns of insulated copper wire of 0·415 millim. diameter (or size No. 26 of ordinary wire-gauge); D is a permanent bar-magnet held in its place by the screws E, E, and having upon its poles two flat armatures of soft iron, F, F, placed edgewise. Within the axis of the coil is a straight wire of soft iron, G, one end of which is held fast by the pillar-screw H, and the other by the cylindrical binding-screw I; the latter screw has a hook, to which is attached a vulcanized india-rubber band, J, which is stretched and held secure by the hooked brass rod K and the pillar-screw L. The screw H is surmounted by a small mercury cup for making connexions with one pole of a voltaic battery, the other pole of the battery being secured to the pillar-screw M, which is also surmounted by a small mercury cup, and is connected with the cylindrical binding-screw I by a copper wire with a middle flattened portion O to impart to it flexibility. The two ends of the fine wire coil are soldered to two small binding-screws at the back; those screws are but partly shown in the sketch, and are for the purpose of connexion with a suitable galvanometer. The armatures F, F are grooved on their upper edges, and the iron wire lies in these grooves in contact with them; and to prevent the electric current passing through the magnet, a small piece of paper or other thin non-conductor is inserted between the magnet and one of the armatures. The battery employed consisted of six Grove’s elements (arranged in one series), with the immersed portion of platinum plates about 5 inches by 3 inches; it was sufficiently strong to heat an iron wire 1·03 millim. diameter and 20·5 centims. long to a low red heat.

scholarly journals The influence of homodromous and heterodromous electric currents on transmission of excitation in plant and animal

1915 ◽  
Vol 88 (607) ◽  
pp. 483-507 ◽  
Keyword(s):  
Electric Current ◽  
The Other ◽  
Muscle Preparation ◽  
Mimosa Pudica ◽  
Electric Currents ◽  
Joint Effects ◽  
Conducting Tissue ◽  
The One ◽  
Conduction Of Excitation ◽  
Stimulation Of

I have in a previous paper described investigation on the conduction of excitation in Mimosa pudica . It was there shown that the various characteristics of the propagation of excitation in the conducting tissue of the plant are in every way similar to those in the animal nerve. Hence it appeared probable that any newly found phenomenon in the one case was likely to lead to the discovery of a similar phenomenon in the other. A problem of great interest which has attracted my attention my attention for several years is the question whether, in a conducting tissue, excitation travels better with or against the direction of an electric current. The experimental difficulties presented in the prosecution of this enquiry are very numerous, the results being complicated by the joint effects of the direction of current on conductivity and of the poles on excitability. As regards the latter, the changes of excitability in the animal nerve under electrotonus have been demonstrated by the well-known experiments of pflüger. In a nerve-and-muscle preparation, the presence of a pole P is shown to induce a variation of excitability of a neighbouring point S. When P is kathode, the excitability of the point S, near it, is enhanced; stimulation of S, previously ineffective, now becomes effective, and the resulting excitation is transmitted to M, causing response of the muscle. Conversely, the application of anode at P causes a depression of excitability of S. Stimulus previously effective now becomes ineffective. In this manner the transmission of excitation may be indirectly modified by the polar variation of excitability of the stimulated point (fig. 1 a ).

scholarly journals I. On a comparison between apparent inequalities of short period in sun-spot areas and in diurnal declination-ranges at Toronto and at Prague

1886 ◽  
Vol 40 (242-245) ◽  
pp. 220-235
Keyword(s):  
Solar Physics ◽  
The Other ◽  
Present Communication ◽  
Diurnal Temperature ◽  
Short Period ◽  
Temperature Ranges ◽  
The One

1. In a report to the Solar Physics Committee (“Proc. Roy. Soc.,” vol. 37, p. 290, 1884) we discussed the relations between certain apparent Inequalities of short periods in sun-spot areas on the one hand and diurnal temperature-ranges at Toronto and at Kew of corresponding periods on the other. In the present communication we proceed to discuss the connexion between the same solar Inequalities and the diurnal declination-ranges at Toronto and at Prague.

scholarly journals The method of meningostomy and its application in the study of the brain in animals

2021 ◽  
Vol 27 (8) ◽  
pp. 820-821
Author(s):  
A. I. Smirnov ◽  
P. D. Olefirenko
Keyword(s):  
Cerebral Cortex ◽  
Electric Current ◽  
Brain Stimulation ◽  
Thermal Effects ◽  
Brain Injuries ◽  
The Other ◽  
Surgical Methods ◽  
The One ◽  
The Brain ◽  
Gain Access

All surgical methods used in the study of the brain in animals can be combined into two groups: 1) methods of direct and indirect shutdown of a particular part of the brain and 2) methods of non-mediocre brain stimulation by electric current or by mechanical, chemical or thermal effects. In the hands of different experimenters, depending on the goals and objects of research, these basic methods varied to one degree or another. All modifications were aimed at, on the one hand, to avoid brain injuries during trepanation as much as possible, and on the other hand, to gain access to the cerebral cortex without exposing it at the time of the observation itself. As can be judged from the literature collected from E. Abderhalden in Handbuch der biolog. Arbeitsmethoden to a certain extent this has already been achieved.

VIII. A critical study of spectral series.— Part III. The atomic weight term and its import in the constitution of spectra

1914 ◽  
Vol 213 (497-508) ◽  
pp. 323-420
Keyword(s):  
Periodic Table ◽  
Principal Series ◽  
Atomic Weight ◽  
The Other ◽  
Critical Study ◽  
Spectral Series ◽  
Present Communication ◽  
The Real ◽  
Real Relation ◽  
The One

The doublet and triplet separations in the spectra of elements are, as has long been known, roughly proportional to the squares of their atomic weights, at least whenelements of the same group of the periodic table are compared. In the formulæ which give the series lines these separations arise by certain terms being deducted from the denominator of the typical sequences. For instance, in the alkalies if the p -sequence be written N/D m 2 , where D m = m +μ+α/ m the p -sequence for the second principal series has denominator D—Δ, and we get converging doublets; whereas the constant separations for the S and D series are formed by taking S 1 (∞) = D 1 (∞) = N/D 1 2 and S 2 (∞) = D 2 (∞)= N/(D 1 —Δ) 2 . It is clear that the values of Δ for the various elements will also be roughly proportional to the squares of the atomic weights. For this reason it is convenient to refer to them as the atomic weight terms. We shall denote them by Δ in the case of doublets and Δ 1 and Δ 2 in the case of triplets, using v as before to denote the separations. Two questions naturally arise. On the one hand what is the real relation between them and the atomic weights, and on the other what relation have they to the constitution of the spectra themselves ? The present communication is an attempt to throw some light on both these problems.

10. The Elementary Composition of Nitroglycerine

1884 ◽  
Vol 12 ◽  
pp. 234-235
Author(s):  
Matthew Hay ◽  
Orme Masson ◽  
Crum Brown
Keyword(s):  
The Other ◽  
Complete Analysis ◽  
Present Communication ◽  
Elementary Composition ◽  
The One

Investigations have been made by Railton, Williamson, Hess and Schwab, Beckerhinn, and Sduer and Ador for the purpose of ascertaining the elementary composition and the constitution of nitroglycerine. They all agree in regarding it as a nitrate of glyceryl; but, whilst some consider that it is a tri-nitrate, others hold that it is a variable mixture of the tri-nitrate with di-nitrate and mononitrate. Their analyses are quite insufficient to establish either the one or the other conclusion, and have mainly been confined to estimations of the nitrogen. If we except a comparative estimation of the carbon with the nitrogen, there exist absolutely no determinations of the carbon or of the hydrogen. And, as the decomposition of nitroglycerine with potash has been shown to occur in a manner considerably different from that suggested by Railton and Williamson, the main reason in support of the constitution of nitroglycerine as a tri-nitrate has been removed. The authors of the present communication therefore believed that they were amply justified in making a fresh and more careful and complete analysis of the composition of nitroglycerine. Absolute determinations were made, not only of the nitrogen, but also of the carbon and hydrogen; and, in order to ascertain the uniformity in composition of nitroglycerine, the nitrogen of samples prepared by various methods was estimated. The nitroglycerine was both pure and thoroughly dried. For the determination of the nitrogen, modifications of Dumas's method and of Schloesing's method were employed. The carbon and hydrogen were estimated by a modification of Liebig's method. Every precaution was taken to insure that the results obtained should be correct. The average of the determinations gave 15 · 91 per cent, of carbon, 2 · 49 per cent, of hydrogen, and 18 · 05 per cent. (Dumas) or 18 · 14 per cent. (Schloesing) of nitrogen. Theoretically nitroglycerine, regarded as the tri-nitrate of glyceryl, contains 15 · 86 per cent, of carbon, 2 · 20 per cent, of hydrogen, and 18 · 50 per cent, of nitrogen. The quantities obtained by experiment agree so closely with the theoretical quantities that they may be regarded as affording proof that nitroglycerine is, in reality, the tri-nitrate of glyceryl. The authors also conclude, from the unvarying amount of nitrogen obtainable from variously prepared specimens of nitroglycerine, including one from Nobel's dynamite, that nitroglycerine is constant in composition and does not contain any of the lower nitrates of glyceryl, unless very imperfectly washed.

scholarly journals Description of the electro-magnetic clock

1843 ◽  
Vol 4 ◽  
pp. 249-250 ◽  
Keyword(s):  
Electric Current ◽  
Copper Wire ◽  
The Other ◽  
Maximum Effect ◽  
Magnetic Coils ◽  
Small Disc ◽  
The Difference ◽  
Electro Magnetic ◽  
Fixed End ◽  
Metallic Parts

The object of the apparatus forming the subject of this communication, is stated by the author to be that of enabling a single clock to indicate exactly the same time in as many different places, distant from each other, as may be required. Thus, in an astronomical observatory, every room may be furnished with an instrument, simple in its construction, and therefore little liable to derangement, and of trifling cost, which shall indicate the time, and beat dead seconds audibly, with the same precision as the standard astronomical clock with which it is connected; thus obviating the necessity of having several clocks, and diminishing the trouble of winding up and regulating them separately. In like manner, in public offices and large establishments, one good clock will serve the purpose of indicating the precise time in every part of the building where it may be required, and an accuracy ensured which it would be difficult to obtain by independent clocks, even putting the difference of cost out of consideration. Other cases in which the invention might be advantageously employed were also mentioned. In the electro-magnetic clock, which was exhibited in action in the Apartments of the Society, all the parts employed in a clock for maintaining and regulating the power are entirely dispensed with. It consists simply of a face with its second, minute and hour hands, and of a train of wheels which communicate motion from the arbor of the second’s hand to that of the hour hand, in the same manner as in an ordinary clock train; a small electro-magnet is caused to act upon a peculiarly constructed wheel (scarcely capable of being described without a figure) placed on the second’s arbor, in such manner that whenever the temporary magnetism is either produced or destroyed, the wheel, and consequently the second’s hand, advances a sixtieth part of its revolution. It is obvious, then, that if an electric current can be alternately established and arrested, each resumption and cessation lasting for a second, the instrument now described, although unprovided with any internal maintaining or regulating power, would perform all the usual functions of a perfect clock. The manner in which this apparatus is applied to the clocks, so that the movements of the hands of both may be perfectly simultaneous, is the following. On the axis which carries the scape-wheel of the primary clock a small disc of brass is fixed, which is first divided on its circumference into sixty equal parts ; each alternate division is then cut out and filled with a piece of wood, so that the circumference consists of thirty regular alternations of wood and metal. An extremely light brass spring, which is screwed to a block of ivory or hard wood, and which has no connexion with the metallic parts of the clock, rests by its free end on the circumference of the disc. A copper wire is fastened to the fixed end of the spring, and proceeds to one end of the wire of the electro-magnet; while another wire attached to the clock-frame is continued until it joins the other end of that of the same electromagnet. A constant voltaic battery, consisting of a few elements of very small dimensions, is interposed in any part of the circuit. By this arrangement the circuit is periodically made and broken, in consequence of the spring resting for one second on a metal division, and the next second on a wooden division. The circuit may be extended to any length ; and any number of electro-magnetic instruments may be thus brought into sympathetic action with the standard clock. It is only necessary to observe, that the force of the battery and the proportion between the resistances of the electro-magnetic coils and those of the other parts of the circuit, must, in order to produce the maximum effect with the least expenditure of power, be varied to suit each particular case. In the concluding part of the paper the author points out several other and very different methods of effecting the same purpose; and in particular one in which Faraday’s magneto-electric currents are employed, instead of the current produced by a voltaic battery: he also describes a modification of the sympathetic instrument, calculated to enable it to act at great distances with a weaker electric current than if it were constructed on the plan first described.

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