THE LARGE INDUCTION COIL. We extract from the Chemical News the following abstract of a paper communicated to the Royal Society, by J. P. Gassiot, F.R.S. : ” The length of the coil from end to end is 9 feet 10 inches, and the diameter 3 feet ; the whole is cased in ebonite ; it stands on two strong pillars covered with ebonite, the feet of the pillars being of a diameter of 22 inches. The ebonite tubes, etc., are the largest ever constructed by the Silver Town Works. ” The total weight of the great coil is 15 cwts., that of the ebonite alone being 477 lbs. ' “ The primary wire is made of copper of the highest conductivity and weighs 145 lbs. ; the diameter of this wire is 0'0925 of an inch, and the length 3 770yards. The number of revolutions of the primary wire round the core of soft iron is 6,000, its arrangement being 3, 6, and 12 strands. ” The total resistance of the primary is 2'201400 British Association units, and the resistance of the primary conductors are respectively—for three strands, 0'733800 British Association units ; six, 0.866945 B.A.U. ; twelve, 0'1834725 B.A.U. ” The primary core consists of extremely soft straight iron wires 5 feet in length, and each wire is 0'0625 of an inch in diameter. The diameter of the combined wires is 4 inches, and the weight of the core is 123 lbs. ” The secondary wire is 150 miles in length ; it is covered with silk throughout, and the average diameter is 0 015 of an inch. ” The total weight of thios wire is 606 lbs., and the resistance is 33^560 B.A. units. The length of the secondary coil is 55 inchlils, and the insulation throughout is calculated to be 95 per cent beyond that required. The secondary wire is insulated from the primary by means of an ebonite tube of t an inch in thickness and 8 feet in length. ” The length of the secondary coil is 54 inches, the diameter is 19 inches, and without the internal ebonite tube containing the primary wire and iron core it is a cylinder 19 inches in diameter and 6 inches thick. ” The condenser, made in the usual manner with sheets ot varnished paper and tinfoil, is arranged in six parts, each con- taing 125 superficial feet, or 750 square feet of tinfoil in tlie whole ” The spark obtained from the large coil is thick and flamelike in its appearance, and therefore it will be alluded to as the 'flaming sparks ” When the discharging point and circular plate are brought within 6 or 7 inches of each other, the flaming nature of the spark becomes still more apparent. ” Two light yellow flames curving upwards appear to connect the opposite poles. If a blast of air from a powerful bellows is directed against a flaming spark, the flaming portion can be blown away and increased in area, and thin wiry sparks are now seen darting through it, sometimes in one continuous stream, at another time divided into three or more sparks, all following the direction in which the flame is blown. ” The flaming spark is very hot, and if passed through asbestos (supported on an insulating pillar), quickly causes the latter to become red hot. ” When powdered charcoal is shaken from a pepper box into the flaming spark in a vertical line and in considerable quantities, the greater part of the light is obscured, and the whole form of the flaming spark presents the appearance of a black cloud with a line of brightly ignited particles fringing the bottom parts. If the charcoal is dusted through in small quantities, each particle becomes ignited, like blowing charcoal into a hydrogen flame ” When the flaming spark is directed on to a glass plate upon which a little solution of lithium chloride is placed, the latter colors the flame upwards to the hight of 8 or 4 inches in the most beautiful manner; and if the point of the discharge is tipped with paper, or sponge moistened with a little solution of sodium chloride, the two colors (the yellow from the salt, and the crimson from the lithium) meet each other, a neutral point being found about half way, and thus illustrating apparently the dual character of electricity, and that + passes to — electrical, and vice versa. The flaming spark can be obtained in perfectly dry air. While passing through common air, if blown against a sheet of damp litmus paper, the latter is rapidly changed red. In order to ascertain whether the acid product was nitric acid, the flaming spark (9 or 10 inches in length) was passed through a tube connected by a cork and bent tube with a bottle containing distilled water, from which another tube passed to the air pump ; on drawing the air slowly. over the spark, and passing the former into the bottle, nitric acid was obtained in large quantities, so much so that it could be detected by the smell and taste as well as by the ordinary tests. The popular notion that nitric acid is always produced doring a thunder storm would therefore appear to be correct. To determine the effect of a cooling surface on the flaming spark, a hole lt inches in diameter was bored through a thick block of Wenham Lake ice, and the spark passed through the air in the tube of ice ; no change took place, and the spark was still a flaming one. ” When the spark was received on the ice, it lost its flaming character, and became thin and wiry, spreading out in all directions. ” If the discharging wires were tipped with ice, the spark vas always flaming when any thickness of air intervened be. tween them. Even over the ice, if the spark passed a frae- tion of an inch above the surface, it was always a flaming one, but changed to th” thin spark when the point of the discharging wire was thrust into the ice. ” If one of the discharging wires of the great coil is brought to the center of a large swing looking-glass and the other wire connected with the amalgam at the back, the sparks are thin and wiry, arborescent, and very bright ; the crackling noise of these discharges being quite different from that of the heavy thud or blow delivered by the flaming spark. ” When the discharging wire is brought close to the flame of the looking-glass, or if a sufficient thickness of air intervenes, the spark again becomes flaming ; or, as sometimes occurs, if the discharging wire is placed about 5 inches from the frame, the spark is partly flaming and partly wiry, i. e., when it impinges on the glass. ” The spectrum isa continuous one with the sodium line. ” When the blast of air is used, and the wiry sparks made apparent, then the nitrogen line appears. ” The flaming spark has been ascribed by some experienced observers to the incandescence of the dust in the air, and especially sodium chloride ” To ascertain whether the ' flaming spark' could be obtained with a small number of cells, the large Bunsen's battery was reduced to three cells, and it was found that no appreciable spark could be proftuced when the whole primary wire was used with less than five cells. ” By reducing the length of the primary wire, and using the four divisions separately, with five cells the spark was wiry, and varied from 4t to 6t inches ; with 10 cells it was wiry, and varied from 8t to 9! ; in the latter the spark was slightly flaming. With fifteen cells the spark was slightly flaming, and varied from 10 inches to 11f inches. With twenty cells a flaming spark varying from 11t inches to 12t inches was obtained. ” When the two wires from the secondary coil are placed in water, no spark is perceptible, even when the wire was brought very close together, until they touch. ” If the negative wire is passed through a cork, on which a glass tube (a lamp glas;;) is fixed containing a depth of 5 inches of water, and the positive wire is brought within half an inch of the surface of the water in the tube, it becomes red hot, and if drawn further away from the surface the upper part of the tube is filled with a peculiar glow or light abounding in Stokes' rays. ” The experiments with the vacuum tube, and especially Gassiot's cascade, are, as might be expected, very beautiful. When a coal gas vacuum tube of considerable diameter, and conveying the full discharge from the secondary coil, is supported over a powerful electro-magnet axially, the discharge is condensed and heat is produced. ” If placed equatorially, the heat increases greatly, and when the discharge is condensed and impinges upon the sides of the glass tube, it becomes too hot to touch, and if the experiment was continued too long the tube would crack. ” The enormous quantity of electricity • of high tension which the coil evolves, when connected with a battery of forty cells, is shown by the rapidity with which it will charge a Leyden battery. ” Under favorable circumstances, three contacts with the mercurial break will charge 40 square feet of glass. ” On one occasion a series of twelve large Leyden jars arranged in cascade were discharged ; the noise was great ; and each time the spark (which was very condensed and brilliant) struck the metallic disk, the latter emitted a ringing sound, as if it had received a sharp blow from a small hammer. ” The discharges were made from a point to a metallic disk; and when the former was positive the dense spark measured from 18t to 1Sf inches, and fell to 2£ inches when the metallic plate Was positive andthe point negative. ” Variations of the Lyden-jar experiments were tried by connecting the coil worked by a quantity battery of 25 + 25 cells 'Yith six Leyden jars arranged in cascade, and the spark obtained measured 8t inches. ” The same six jars' connected with the coil, when the fifty cells were arranged continuously for intensity, gave a spark of 12 inches of very great density and brilliancy. EarthquaKe-Proof Buildings. The recurrence of earthquake shocks in California has led to a discussion of the methods of building houses in .such a manner as to be virtually earthquake-proof. A San Francisco architect, Mr. Saeltzer, has read a paper on this subject before the California Institute of Architecture, in which he contends that. flexible materials only should be used in building. His theory is as follows : ” By distributing the whole weight of the building on piers of stone, brick, or iron, or on wooden piles—in fact, isolating the foundation in such a manner that these piers or piles form part of the foundation — and by connecting ! them with iron beams screw-bolted together, the building is then well anchored at the proper place; in fact, this style of found-, ation will form a girding all round the building longitudinally and transversely. ” This mode of construction will insure, first of all, the least contact with the earth ; Secondly, concentration of the whole mass of the building on single points only with strong anchorage; thirdly, more elasticity of the foundation, and consequently more elasticity in the whole mass of the building; fourthly, a combination of heterogeneous materials in one mass—au amalgamation—one of the most important points to be gained; fifthly, this style of building is the cheapest of all, and in most cases applies to our wants and climate, and to the desired architectural arrangements, and is applicable to any material.' ' ** * “ The advantage of the concentration of the whole mass on piers will at once be visible. A pier has more elasticity than a solid wall, and if placed isolated, in the proportion of about eight times the hight to its base, this pier would, by a slight movement of the earth, lose its point of gravity ; but by connecting a number of piers horizontally, traversely, and longitudinally, and by resting the weight of the whole building upon them, they become restrained in their natural action till the whole mass of the building begins to move. ” That piers will facilitate the rapidity or velocity of the movement of the whole mass, nobody will deny ; inasmuch as they stand isolated, are comparatively weake£ than a solid wall, and have solely to depend on themselves, in their own strength and nature, without any assistajjce from a connecting wall. It is hardly necessary to mention that the piers should, of course, be in proportion to the weight they have to support, and should be placed at proper distances for security."_ ** * “To many it may seem strange that the towers of San Francisco stood so well during the late earthquakes, with hardly any apparent damage, and that also in European cities the towers have also been less injured; a fact which proves, in a most striking manner, that the flexibility or elasticity of a mass is a necessity for safety. A tower is a pier of high proportion, and forms a high pendulum, and naturally swings with more rapidity than a longer mass, and hence there is less danger. The tower of the Doin of Erfurt, at present a fortifred city in Prussia, contains the largest bell in the world except the celebrated bell in Moscow. This bell requires twenty-four men to set it in motion, and when in motion has always caused an oscillation of the tower varying from four to five feet from the perpendicular line. For centuries this bell has been used, and the tower remains as per- feet as ever. This tower is built of cut stone, with the finest details of Gothic architecture. I merely give this example to show the flexibility even of stone, provided tho proportions are right. ” All our hotels stood well, also a large number of stores ; in fact all buildings supported on piers or columns. All the bodies of churches also stood well, especially where buttresses were introduced. Each buttress forms a pier, and has, consequently more elasticity, and always will stand well, provided the proportions are artistically carried out. Very low ' churches, built more in the proportions of a stable, are unsafe ; in fact, all buildings one story high and of considerable extent are liable to danger, more so than two or three-story buildings, no matter of what materials soever.' ' . 276 ^tmixiii SMMATL [OCTOBER 30, 1869. Floating Telegraph Station and lightship. We gave on page 36, Vol. XVII., a description with illustrations of floating batteries, buoys, and lifeboats, invented Oy Capt. John Moody, late Managing Director of the Goole Steam-Shipping Company. We now present to the consideration of our readers an improvement on the form of the lightship, an engraving of which was given in the article referred to. The great difficulty to be overcome in the perfection of this invention was to obtain a suitable vessel capable of being moored in any sea however tumultuous, and to obviate the continuous rolling motion of the lightships hitherto used, the great essential in a floating telegraph station being buoyancy with stability and constant steadiness, which a sharp vessel canriot give. The vessel is constructed with four equal rays or projections proceeding from a central circular deck protected by iron bulwarks, sloping outward at the top. Proper openings are made through the deck to the interior of the vessel for' companions and skylights, as well as good large seupper holes round the bulwarks to take ofiT all water from the deck, so that even if it were possible for this part of the vessel to fill with water it would all run out through the scuppers ; nor would there be any danger of foundering, owing to the great buoyancy of the vessel, her clearing valves, and her division into numerous water-tight compartments and other internal contrivances. The vessel is also constructed to deflect the waves as they strike, instead of allowing them to break upon deck, [IS in the ordinary form of vessel. It is proposed by the inventor to use these vessels as intermediate telegraph stations where long submarine cables are laid. For example, he would, in establishing an Atlantic cable, carry it in comparatively short lengths, placing one of these vessels somewhere in mid-channel with a cable from band's End. The next vessel would be placed off the Western Islands, or Hebrides, and the third off' the American coast,from which a cable would be carried direct to New York. By this means the cable would be divided into shorter lengths without increasing its aggregate length, and it is claimed the following advantages would be secured : ' 1. The diameter and weight of the cable would be considerably lessened, thereby diminishing its cost. 2. These shorter lengths could be carried out and laid by a smaller steamer than that employed in laying the present cables, thus very considerably reducing the cost of laying them. S. These shorter cables, should they break, could be repaired or replaced with new lengths in a much shorter time, with much less labor, and at a greatly diminished risk and cost than in the case of a cable stretching from shore to shore. Capt. Moody claims that even supposing that the cable laid in lengths was only intended to be used at its shore ends for through messages, such a plan would possess the advantages enumerated; but he claims numerous other advantages for this system. Among these later advantages are the following : Ships could call, and masters could communicate with their owners, whether in England, France, or the Continent, on that side the cable, or in America on this side. Masters on a trading voyage, and a long time out, would thus be enabled to send home letters and papers giving full information of the results of their voyages; for these mid-ocean stations could be made available for post-offices as well as telegraph stations. Arrangements could be made with the mail steamers to call for letters and anything else that might be left at the stations. By means of these stations, money and bills could be transmitted from masters to owners. Large quantities of all kinds of stores and provisions could also be kept there for sale to passing ships, and to relieve shipwrecked people who might be picked up, or who ia open boats had succeeded in gaining the station. News of wrecks or disasters at sea could be sent through the cable, and assistance might be obtained for many a ship which otherwise would be lost. Lifeboats should be kept at these stations (built upon the same principle as the telegraph ships, somewhat modified—that is, with four rays or arms, which would render them free from liability to upset), for the purpose of saving life, rendering salvage services, and as a means of communication with passing ships; so that all these floating stations would thus become not only places of business, but places of refuge in the very midst of the ocean. These stations coul.d be boarded in all weather, for from their peculiar form they could always be approached on the lee side, where the sea would be much broken, and perfect safety in boarding secured. In fact these stations might be made the centers of communication between all nations by a simple system of cross cables; as, for example, in a cable between Europe and America, the first or mid-channel station might have short cross cables to England and France, the next station, placed off the Western Islands, could have a short cable carried to the principal island in the group, putting it in communication with America, England, France, arid the whole Continent of Europe ; and what could be done in tliat case in that ocean, could be done in all other cases, and in all other oceans and seas, Until the whole world became connected together.
This article was originally published with the title "Some Experiments with the Great Induction Coil at the Royal Polytechnic" in Scientific American 21, 18, 275-276 (October 1869)