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After studying the question for a long time, Andrée finally decided to give his balloon the cubical contents of 158,924 feet, and the shape of a sphere terminating in a slightly conical appendage.

This sphere, fitted with two lateral regulating valves, one lower automatic valve, and a “rending flap,” measures 22 yards in diameter, by 1,431 yards surface; it is enclosed in a net of hemp cord, terminating in systems of “crow feet,” and suspending ropes attached to the car by means of a “load ring.”

The upper part of the balloon is protected against rain and snow by a varnished silk cover, the apex of which is fixed to the upper pole of the envelope, and the lower margin to the meshes of the net.

The Envelope.—In making up the envelope, 600 pieces of best quality Pongee silk, each from 18 to 19 yards long by about 18 inches wide, were used. From each of these a piece was cut off which was tried in both directions—that of the chain and that of the weft; then the pieces were classified according to their strength, in order to be subjected to the operation of cementing or joining together.

All these pieces, after being cemented together, were tried again before being used. The trials were made by means of a Perreaux dynamometer, with strips about 2 inches wide by 4 inches long, under the control of Messrs. P. de Nordenfeld and Noël, engineers of the Nordenfeld Company, to whom Andrée had entrusted the task of testing the materials used in the construction of his balloon.

VIEW OF THE LOWER PART OF THE BALLOON.

The tests gave the following results:—For double tissue, the breaking strains varied from 5,291 lbs. to 7,936 lbs. per yard, for threefold tissue from 6,854 to 12,125, and for fourfold tissue, made up of the best single pieces found, from 13,227 to 15,873 lbs. per yard.

The minimum resistance demanded by Andrée was fixed at 2,204 lbs. per yard and per single thickness of Pongee. This minimum was therefore greatly exceeded.

The cemented pieces were classified according to their strength, for distribution over the surface of the balloon as the strain demanded.

The upper part of the envelope is a disc 19 feet 8 inches in diameter, formed by twenty-four widths of fourfold silk. The adjoining part, consisting of threefold silk up to 13 feet 1 inch below the equator of the sphere, is composed of forty-one zones made up of forty-eight widths each.

The remainder of the balloon, down to the lower parallel, having a diameter of 23 feet, is of double material, being made up of twenty-two zones of forty-eight widths; and finally the lower part, including the appendage, is of threefold silk, and consists of five zones of forty-eight widths, and three zones of twenty-four widths each.

The portions made up of threefold and double Pongee are joined together by an intermediate zone in which the various widths of material are alternately made up, half of threefold and half of double tissue.

In each zone the various widths, or pieces of material, are identical in shape; twenty-seven different templates had to be designed in order to determine the exact shape of the various pieces or widths of material, the total number of which is 3,360. The cutting out of these pieces was effected with the aid of a cutting blade guided by a steel rule, following the outlines of a template. At first those belonging to one and the same zone were joined together, and the zones were then joined so that the various pieces or widths overlapped each other in such a manner as to give the balloon the aspect of a structure of bricks or freestone.

The cemented joints of the various pieces are ½ inch wide; they are then sewn by a machine, with three seams made with fine silk in the double or threefold material, and four rows of stitches in the fourfold material.

These joints or seams are then covered, outside and inside, with a strip of single silk 1⅕ inches wide, cemented on with a special varnish recently discovered by M. Lachambre.

The strips cemented by this new process have the double advantage of rendering the seams impermeable and restoring to the joints the resistance of which the stitching deprives them.

The varnish used for this cementing meets all requirements; it preserves the natural suppleness of the material, is unaffected by the balloon varnish, which has linseed oil for its basis, and is proof against water and changes of temperature.

The tests made with the joints thus constituted, proved that their resistance was greater than that of the adjoining parts, and Andrée, who only desires an equal strength throughout, naturally was very well satisfied with this result.

The seams are 4,811 yards long, with three or four rows of stitching, representing a line of single stitching equal to a length of 15,310 yards, and the total length of the cemented strips is nearly 9,842 yards.

The two hemispheres of the balloon were first formed; their weight was 2,116 lbs., and before proceeding to the last equatorial closing seam, they were given three coats of Arnoul’s varnish (the best balloon varnish hitherto tried); a fourth coat being given after the two halves had been joined together, on the premises of the “Palais du Champ de Mars,” remaining from the 1889 Exhibition.

Net.—The net of the polar balloon is composed of 384 hemp cords, ⅙ inch thick by 211 feet 7 inches long, each having a breaking strain of not less than 873 lbs. (in the tests made the minimum result was 925 lbs., while the maximum was 1,190 lbs.).

Each cord is jointless; its two ends are fixed, at the upper pole, to a cordage ring or crown measuring 26 inches in diameter and 2⅓ inches in thickness. There are no knots in this net, the cords being interwoven at their crossing points, one being passed through the other; it was in this way that the “Henri Giffard” captive balloon was finished in 1878.

The crossing points are strengthened by ligatures of fine twine.

VALVES FOR WORKING THE BALLOON.

The circumference of the net, all the way up, consists of 192 meshes, the dimensions of which vary according to the area of the zone they are to cover. These meshes, the number of which is no less than 19,000, represent a length of twine amounting to nearly 16,404 yards.

The lower part of the net is formed by a system of three zones of crowfeet or cringles, each zone reducing, by one-half, the number of meshes composing the next upper zone.

The first row of crowfeet is mounted on thimbles of nickeled brass, the second and the third on wooden pulley-blocks, having sheaves of lignum vitæ; and forty-eight suspending cords, each fitted at its end with an eye, complete the net and form points for tying it to the retaining ring by means of toggles. These suspending cords have a diameter of ⁷⁄₁₀ inch, and a bearing-strain of no less than 6,613 lbs.

The net thus constituted weighed 776 lbs. In order to preserve the cordage from moisture it was impregnated with vaseline, except in the upper part, which was covered with a projecting cover of varnished silk; after this operation the weight of the net was 974 lbs.

Eight detachable equatorial cringles were fixed to the equator of the net. They were to serve for holding up the balloon, and preventing it from oscillating, in the shed which was to shelter it at Spitzbergen, while awaiting a favourable wind for the departure of the expedition.

Protecting Cover.—A spherical calotte of single silk, varnished with four coats and vaselined, and having an area of 1,560 square feet, covers the upper part of the balloon. It is finished in the same way as the balloon, being composed of overlapping widths to the number of 720.

The seams, having a width of ¼ inch, are hooked together, and sewn with two rows of stitching with silk thread. They are not covered with cemented strips. Their total length is 656 yards.

The vertex of the protecting cover, of conical shape, is of double silk. It rests on a small wooden structure, likewise of conical shape, the base of which, placed on the material at the upper pole of the balloon, is surrounded and held in place by the crown of the net.

The lower zone, terminating the protecting cover, is of double silk. Its extreme edge is put round a hemp bolt-rope, ³⁄₁₀ inch in diameter, which is sewn into the material; ninety-six eyes made above this bolt-rope are intended to receive thongs for fixing the protecting cover to the meshes of the net.

This protecting cover weighs 88 lbs. Its object is to protect the top of the balloon against rain, and more especially to prevent incrustation with snow between the meshes of the net.

Valves.—The balloon has no valve at the top, because its action would probably be affected by snow; but it is provided with two manipulating valves, of equal dimensions, one being placed at the equator, and the other one metre above the equator. These are at 150 degrees angular distance from each other.

These valves, constructed on a system of Andrée’s, measure 9⅘ inches in external diameter. Each is formed by a disc of aluminium bronze, 9 inches in diameter, and under normal conditions rests on a circular piece of walnut wood, but can be withdrawn therefrom by moving it along a screw which occupies the centre. This movement is effected from the car of the balloon by means of two cords for each valve, passing through the interior of the balloon and issuing from it near the appendage through four tubes, arranged in pairs.

Gas-tightness is obtained by a circular rubber band, against which the outer margin of the valve disc rests. The orifice for the escape of gas measures 7⅘ inches in diameter. In order to fix the valves to the balloon, two openings, 7⅘ inches in diameter, are made in the material. The margin around these openings is strengthened by collars, 19⅖ inches in diameter, of threefold material, cemented and sewn on; the seat of each valve is applied internally to the material of the balloon, the margin of which is caught between two rubber bands, and thereupon pressed against the seat by an external wooden hoop and bolts.

These valves do not present any external projection against which the cord of the net might catch.

The automatic valve closing the appendage was suggested to Andrée by M. Lachambre, and was adopted. It measures 39 inches in external diameter, with a discharge orifice 34 inches in diameter. The valve disc, of threefold Pongee silk, is 35⅘ inches in diameter. It is provided with two glazed windows, in order to enable the aeronauts to inspect the interior of the balloon. This disc, which is slightly conical, is fitted upon a walnut-wood ring, which acts as a seat, in which it is held by the traction of six spiral springs of steel wire, fastened on one side to the end of the wooden spokes of the valve, and on the other side to the top of a small frame fixed on the seat. The frame, mounted on the wooden ring or crown, is formed by twelve nickeled steel tubes.

The valve is guided in its course by a central steel tube, sliding in another tube, which serves as an axis for the frame. A small cotter limits its action, the length of which is equal to one-half of the radius of the discharge orifice. The joint is rendered gas-tight at the periphery of the valve by means of a brass blade resting on a rubber band stretched in a groove of the seat.

The valve commences to open under the action of an internal pressure corresponding to ³⁄₁₀ inch water column. In order to fix it to the balloon, it is placed in the interior of the appendage, the margin of which, held between two rubber bands, is kept tight against the seat by an external belt or ring of brass, fastened by bolts.

“Rending Flap.”—The rending flap is 4½ yards high, and has a surface of 4⁷⁄₁₀ square yards. It is formed of threefold Pongee silk, and is rectangular in shape, terminating in a curvilinear triangle, the point of which is turned upwards. Its vertical axis is at an angular distance of 105 degrees from each of the two manipulating valves; the lower base, which is 35⅖ inches wide, reaches down to 19⅗ inches above the equator. The seams joining the material of the “rending flap” to that of the balloon are similar to the seams of the various widths, and are likewise covered with cemented strips.

In the interior of the balloon the upper extremity of the “rending flap” is of fourfold silk; its edge is put round a stick of hard wood, to which a rope for pulling is fixed, by means of which the rent is made. This rope descends to the car after having passed through the lower part of the envelope, near the appendage, in a tube.

In order to make the rent with ease, which will require an effort equal to a traction of about 220 or 250 pounds, Andrée intends to use a small grapnel, which he will attach to the end of this rope and throw to the ground at the proper moment.

THE BALLOON IN THE 96 FEET GALLERY OF THE CHAMP DE MARS EXHIBITION.

Thereupon the balloon will be emptied very rapidly, and all dragging along the ground will be avoided, however violent the wind may be.

Of course Andrée will not make use of the “rending flap” until he is travelling over hospitable regions and wishes to terminate his aerial voyage and alight definitely.

Bands for Protection against water.— Sundry Details.—Above the appendage, at the parallels measuring 16 feet 4 inches and 22 feet 11 inches respectively in diameter, there are fixed, by one of their edges, two vertical circular bands nearly 4 inches high.

These bands are of single silk; their purpose is to form gutters for carrying off any water which might run down the material of the balloon, and thus protect the car in which the observers are stationed from rain. In the interior of the appendage there is another band, differently placed, forming a circular trough, intended to receive any water that might result from a strong condensation of the gases contained in the balloon, and thus prevent any accumulation of such water over the automatic valve. Between the external band, of 16 feet 4 inches in diameter, and the appendage, and facing the tube through which the rending cord passes, the inflating nozzle, which is 19 feet 8 inches long, is fixed.

The two cords which control each of the manipulating valves are worked by pulling: one, being that which opens the valve, is painted blue; the other, which closes it, retains the natural colour of the hemp.

The cord acting upon the rending flap is coloured red.

Along a meridian traced on the envelope coloured marks are made, with figures indicating every 546 yards of cubic contents of the segment above each mark. This will admit of the progress of inflation at Spitzbergen being rapidly ascertained.

On two other meridians, suitably situated, are shown the positions for the straps to support the sails with which the polar balloon is to be provided.

The Car.—In the construction of the car, the use of iron or steel was prohibited, so as to avoid interfering with the action of the magnetic instruments. Its form is cylindrical, measuring two metres in diameter, from centre to centre of its sides, which are of cane basket-work mounted on a framework of chestnut-wood; eight handles of wicker-work are attached to the cylindrical part, at a convenient height, to facilitate the transport.

The bottom is strengthened by wooden crossbeams placed externally and fastened to the basket-work by bolts and brass plates put on the inside.

The cylindrical part is truncated on one side, having a plane surface which is to form part of an inclined plane intersecting the lower floor of the car, and extending from this floor to midway up the cylinder, the length of the chord formed by the plane intersecting the base being 51 inches.

When the balloon touches the ground, rolling of the car will be avoided by this flat surface, which will rest and drag on the ground. Internally, the upper margin of the side is fitted all round with about 100 cords terminating in buckles or eyes. To these cords, which are passed through the basket-work, instruments and various objects are to be attached. The roof of the car is a disc or cover, likewise of basket-work, slightly convex in order to prevent any accumulation of water. The margin of the periphery of this cover forms a cavity into which the margin of the car is inserted, thus preserving its peculiar shape. Cross-pieces of wood fixed inside the cover or roof impart to it the necessary rigidity to support the observers; entrance to the car and exit therefrom is effected by means of a trap-door which moves on hinges.

Above the flattened part, the cylindrical side of the car is fitted with two square windows with glass panes of 5¾ inches side; the bottom of the car has two square openings of 7⅘ inches side, closed by wooden trap-doors.

The car is covered with tarpaulin having openings corresponding to those in the basket-work.

The tarpaulin of the roof forms a vertical rim 3⁹⁄₁₀ inches in width, perforated with holes for draining off rain-water. The car is suspended by six hemp ropes 1¹⁄₁₀ inch thick. Their respective strength is from 17,636 lbs. to 19,841 lbs. They are interwoven with the basket-work, and joined together at the bottom of the car by a hexagon of rope.

START OF THE VIRGO FROM GOTHENBURG, 7TH OF JUNE, 1896.

Above the roof they are joined to each other by five horizontal ropes placed at equal distances and forming a kind of balustrade 3 feet 3 inches high, which was to be covered in later on either with tarpaulin or some other enclosing material.

The thickness of these horizontal ropes is ⅕ inch, except the uppermost rope, which is ³⁄₁₀ inch thick.

About 6 feet 6 inches above the roof, the hexagon formed by the six ropes is drawn together by a hexagon of rope-work measuring 3 feet 3 inches inside diameter.

The upper end of the suspending ropes terminates in an eye or loop joining it to the ropes of the load ring.

On the circumference of the upper edge of the car six brass balls are fastened, at equal distances from each other, forming the lower part of a system of ball links which are to carry a structure intended to support the scientific instruments. This structure was made at Stockholm under the supervision of Andrée.

The fitting up and equipment of the car was also carried out under his supervision.

The aeronauts will generally be on the flooring of the roof, for the purpose of observations. The interior of the car forms their sleeping apartment, where they will each rest in turn.

Marks of the Expedition.—All the articles comprising the aerostatic equipment are marked with the words “Andrée’s Polar Expedition 1896,” which are branded upon wooden articles, engraved on metal articles, and painted with a durable paint on the protecting cover, the envelope, the tarpaulin of the car, and the ballast bags.

Some ropes of the net and the suspending rope are fitted with small plates strongly fixed to them, on which the above mark is engraved.

The articles not affording sufficient space for the whole mark bear the abridged mark “Aée’s Exp 1896.”

The following articles were made at Stockholm; viz., the “load ring” connecting the balloon with the car, the provision basket, the guide-ropes, sails, etc., as well as the plant for making pure hydrogen gas, a description of which will be found later on. Only the gas conducting pipes, which are of silk, and the ballast bags, were manufactured at Paris, being supplied from the Vaugirard factory.

Exhibition of the Equipment and Plant at the Champ de Mars (Old Buildings of the 1889 Exhibition).—The order for the articles described above was given by Andrée to M. H. Lachambre at the end of December, 1895, and delivery was to be effected between the 15th and 20th of May, 1896, failing which the contractor made himself liable to an enormous progressive fine, in proportion to the number of days of delay, and if delivery was not made before the 3rd of June the order could be cancelled. But the work was executed within the stipulated time, and towards the end of April the whole plant was conveyed to the Champ de Mars, into the 30 m. gallery, in order to be examined there by the Commission.

According to a clause of the agreement the envelope was to be inflated with air, and before the last varnishing to be submitted to an internal pressure equal to 3 inches water-column.

This trial took place on the 3rd of May, in the presence of Messrs. de Nordenfeld, engineer of the Nordenfeld Company, Gaston Tissandier, Colonel Renard and Commander Renard, managers of the Central Establishment of Military Aerostation of Chalais-Meudon. The openings of the balloon were provisionally closed; the valve in the appendage was replaced by a wooden hoop covered by a disc of material containing a glazed window, 7⅘ inches in diameter, thus permitting inspection of the interior of the balloon. The latter was inflated by means of a ventilator supplying about 70,633 cubic feet of air per hour.

Andrée’s experts, who had followed up the manufacture step by step, then examined minutely all the parts, and declared the material to be faultless, and quite in accordance with the desires expressed by Andrée.

After this examination, which showed that the envelope inflated with air did not lose its contents to any appreciable extent, the balloon was emptied, and was then given the last coat of varnish. This having been done, it was again inflated for the purpose of drying.

The net suspended by the crown, in the centre of the central dome, and with the suspending ropes attached to the balustrade of the first gallery, presented the appearance of a vast tent, the summit of which was 131 to 164 feet above the ground.

STAFF-OFFICERS OF THE EXPEDITION.

The car, the valves, and in short all the articles made at Paris were exhibited at the Champ de Mars. A little balloon of 1,148 feet, fully equipped, and inflated with air, suspended by the side of the polar balloon, served for comparison. This exhibition, which was not arranged with a view to profit, was thrown open to the public from the 10th to the 14th of May.

The 10th of May was reserved for special guests, and M. Félix Faure, President of the French Republic, was the first visitor. He took much interest in the various parts of the balloon, which he examined at length, and in the details of its construction. He expressed his best wishes for the success of this interesting expedition.

There were present at the same time as the President, M. de Nordenfeld, Swedish engineer, M. Gaston Tissandier, Colonel Renard, and Commander Renard, who had also watched the work in its various stages, and had co-operated therein to a certain extent.

The Swedish colony was represented by M. Dué, minister plenipotentiary, and Gustav Nordling, vice-consul.

Among the other guests were Messrs. Poubelle, Prefect de la Seine, Admiral Sallandrouze de Larmornaix, General Mathieu, M. Decauville, senator, M. Coulet, solicitor to the Swedish Legation, etc.

During the next four days over 30,000 persons came to see the North Pole balloon, and expressed their good wishes for the success of the three bold Swedish explorers whose courage is universally admired.

A. M.