capture and destroy Berber, and the intended sending of Colonel Stewart and the English consul, Mr. Power, to report to the English Government all that had occurred, and convey his opinions on the situation and the plans to be pursued. The capture of Berber was a manœuvre undertaken for the purpose of opening the river route and enabling them to descend in a steamer to Dongola. With three steamers and four nuggars Berber was shelled, and the rebel fire silenced, enabling them to pass the fort in safety. At Abu Hamed the escort was sent back to Khartoum. Colonel Stewart and the English and French consuls then proceeded with a large party of refugees in a steamer and two nuggars. Overtaken by the rebels, they cut loose the boats. Near the fourth cataract the steamer was wrecked on a rock. The whole party, except two natives, were killed by the Arabs after reaching land. The sheiks offered them hospitality, and then treacherously massacred them.

Gordon, in an answer to some dispatch from Cairo, asking why he did not retire from Khartoum, said, July 31, "I stay at Khartoum because the Arabs have shut us up and will not let us out," declaring: "I repeat, I have no wish to retain this country. My sole desire is to restore the prestige of the Government in order to get out garrisons, and to put some ephemeral government in position in order to get away." The position was critical at this time, for food was running short, and the soldiers were evidently discontented. In the dispatch of August 26, be asked that £300,000 be sent immediately, so that he could give them more satisfactory pay than the paper notes. The remainder of the treasure that Gordon was to take with him into the Soudan, £150,000 in all, was sent after him as far as Berber, where it fell into the hands of the enemy. His situation, through military successes and the capture of provis ions, continued to improve after the departure of his ill-fated companions. The rebels soon raised the siege. On the 6th of October Gen. Gordon, with three steamers and eighteen nuggars, bombarded and captured Shendy and Metemneh. Berber and Djalyeen were also taken, and a force was detailed to occupy Berber under the command of Kashmil Mous Pasha. The town was afterward burned. During the first six months of the siege, Gen. Gordon facilitated the escape down the Nile of about 600 soldiers, mostly invalids, and 2,000 officials,. merchants, etc., including their families and dependents. The refugees were received at Korosko by Giegler Pasha, and looked after at Assouan by Col. Duncan.

Movements of the Mahdi.-The Mahdi threatened to advance upon Khartoum after the arrival of Gen. Gordon. The time when he could move a large body of troops soon passed by, because he could not take them away from their work in the growing season. He was prevented by formidable rebellions against his power in Kordofan. The many wives that he

took to increase his political importance and social influence impaired his sacred renown. He was scoffingly nicknamed the "bridegroom.' He had to withstand a conflict with the not numerous but still formidable people of Takale, who never recognized his divine mission. He put to death their former king and their religious chief for that reason. The people proclaimed the next heir king, and swore revenge, while the Mahdi set out in the spring to destroy the Takalese. The head sheik of the Kabbabish, Saleh, was a more powerful adversary. Saleh's brother, the former sheik, was treacherously murdered by Mohammed Ahmed out of jealousy of his influence. This act turned against the Mahdi the most numerous Arab tribe in the Soudan. Saleh bound his right hand to his breast, vowing that he would only unloose it to strike off the Mahdi's head. Mohammed Ahmed made an enemy also of the slave-dealer, Abd-el-Samat, who had in his service several thousand brave soldiers, by demanding tribute from him after promising him immunity from all contributions. Gen. Gordon's successes at high Nile, and the abandonment of the siege by the neighboring tribes, induced the Mahdi to send troops to Khartoum. As soon as the harvest was in, he moved the bulk of his available army, reported to Zebehr Pasha in August as 100,000 strong, with the intention probably of taking Khartoum and then meeting the English army of relief. He left behind only a small force under Mahmoud Abd-el-Kader, in El Obeid. A rising of the Kabbabish Arabs caused him to turn back, when he set out in October. Before the 1st of November he invested Khartoum with a large army. To his demand for a surrender Gen. Gordon replied that he would hold the place twelve years. The neighboring position of Omdurman was taken from Gordon after some fighting. Gen. Gordon was said to have destroyed the greater part of Khartoum, inclosing the remainder in a fort with a high watch-tower, to be making his own powder, and still sending out his steamers on the Blue Nile as far as Sennaar.

The progress of the rebellion was not achieved by the movement of military forces. The Mahdi has no standing army, and makes no assumption of temporal sovereignty. He relies more on proclamations and missionaries than upon the exhibition of power. At first dervishes and emissaries appear singly in a neighborhood. They preach the restoration of Islam in its purity, promise the abolition of illegal taxation, and unfold the object of the movement, which is the expulsion of the foreign rulers. When the people have been worked up by this means, a quantity of arms are sent. Some Arab tribe is found ready to begin overt action and form the nucleus of an insurgent host. When the revolt is in full progress a lieutenant of the Mahdi comes with arms and ammunition, takes command, and develops an army and a plan of action.

cause.

Gen. Wolseley's Expedition. The English ministers in their course toward Gen. Gordon were guided by the political and financial reasons that impelled them to force upon the Egyptian Government the policy of abandoning the Soudan. They were inclined at first to repudiate their envoy, on the ground that, in establishing military rule at Khartoum and undertaking military operations, he had exceeded his instructions, which directed him to use pacific means only. When they first called Gen. Gordon into consultation he expostulated against the abandonment of Khartoum as injurious to Egypt, to commerce, and to the anti-slavery They assumed that he was now aiming at the restoration of Egyptian authority in the Soudan, or that that would be the result of his successful defense of Khartoum. They would have been glad for him to retreat, but he refused to leave to their fate the 60,000 people whom he was sent to rescue. Every one but the Government recognized the necessity of Gordon's defensive operations, and the perils of his situation. His defense of Khartoum, coupled with the belief that he was backed by the military power of England, was of great service in arresting the tide of rebellion, which threatened to sweep into Egypt. The Government was nevertheless averse to an expedition for his relief, because if English blood and treasure were spent in the Soudan the policy of abandoning the country might have to be given up, and the English protectorate in Egypt might be indefinitely prolonged. The apathy shown regarding the fate of Gordon subjected the Government to telling attacks from the Opposition and wide-spread popular displeasure, not confined to the friends of annexation. At length Mr. Gladstone acknowledged an obligation to look after the safety of Gen. Gordon, and of those who had incurred greater danger by attaching themselves to him, while disclaiming any responsibility for the other Egyptian posts in the Soudan, or any intention to resist the rebellion of the Mahdi, which he described as the movement of a people rightly struggling to be free." On April 28 a dispatch was forwarded to Gen. Gordon by a variety of channels, in which he was desired to advise as to the time, route, and strength of a relief expedition. Not receiving an answer before the adjournment of Parliament, Mr. Gladstone asked, August 5, for a vote of credit of £300,000 in approval of an expedition in the autumn. A relief expedition was arranged the same month on plans drawn up by Lord Wolseley. Although all authorities on Egyptian topography pronounced the Suakin-Berber route the quickest and easiest to Khartoum, the Government would sanction none but the Nile route, as most in harmony with their purpose to confine their operations to the rescue of Gen. Gordon and those involved with him. Gen. Wolseley suggested small boats for river transport beyond Wady Halfa, such as he had employed in his Red

river expedition in Canada. As Gen. Stephenson, commanding the army of occupation, objected to this scheme, Lord Wolseley was asked to take command of the expedition himself, and decided on an expeditionary force of 10,000 men as sufficient for his purpose. He arrived in Egypt September 9. The small boats were built in England and Egypt, and a body of 500 Canadian boatmen and 300 Kroomen from the west coast of Africa engaged. In his letter of instructions, dated October 8, the object of the expedition was stated to be to bring Gen. Gordon and Col. Stewart away from Khartoum. Unless it was necessary for him to penetrate to Khartoum for this purpose, he was not to advance beyond Dongola. That was the sole definite object, though with regard to leaving an organized government behind, Gen. Wolseley was instructed to enter into treaty with the local chiefs, and to promise them liberal subsidies from the Egyptian Government if they would engage to preserve order, and keep down the slave-trade between Wady Halfa and Khartoum. He was prohibited from advancing beyond Khartoum for any purpose, even for the relief of the garrison at Sennaar, which was within easy access on the Nile. The boats, 800 in number, were light enough to be carried around the rapids, and designed to convey each ten soldiers with foodsupplies for 100 days. Stern-paddle steamers, made in sections, were ordered for towage in the clear spaces of the river. Sir Evelyn Wood proceeded to Wady Halfa to superintend the preparations for transport and the collection of stores. It would have been possible at high Nile to draw steamers of not over five feet draught over the cataracts. One steamer, the Nassif-Kheir, was got through with great difficulty in the beginning of September. It was high water about the middle of August. Before the transports, commissariat stores, etc., were prepared in Lord Wolseley's thorough manner, the Nile had fallen so that the elaborate arrangements for river-transport were almost useless. The general-in-chief arrived at the second cataract October 5. The passage up the river from Sarras, where the Canadian double-bowed whale-boats were put into the water, and Dongola, was slow and toilsome. Nile nuggars were found as useful at least as the small boats. On the 20th of November, with 16,000 British troops in Egypt, there were only 3,000 south of Wady Halfa, of whom about 1,000 had reached Dongola. By December 10 there were 10,000 south of Korosko; on the 16th Lord Wolseley joined the advance body under Brig.-Gen. Sir Herbert Stewart at Korti. Here Gen. Wolseley decided to abandon the river route and cross the Bahiuda Desert to Shendy, 180 miles. Gen. Stewart started with 1,000 men on camels December 30. He occnpied the wells at Gadkul, 97 miles from Korti, January 3, and, leaving the guards intrenched there, returned for re-enforcements and supplies, setting out again on the 8th with a corps

am in this lamp, were exhibited. This mineral is found in large quantities in Henderson Co., N. C., where it was first brought to light, and then thought to be worthless. Since it has exhibited the remarkable property of being infusible, it can be used instead of the more expensive metal, iridium.

The enormous lamp on the top of the tower had an arc that leaped three quarters of an inch, the carbon-rods being also three quarters of an inch in diameter. Most of the arc-lamps in and around the building were surrounded by opal or ground-glass globes, for the purpose of diffusing the light. The arc-lamps that illuminated the fountain were so arranged that sheets of colored glass could be interposed, in this way coloring the fountain and producing many beautiful effects. The principal lighting within the building was also done by arc-lamps, they being strung along each of the high arches supporting the roof. The illumination throughout the building was as brilliant as sunlight.

Incandescent Lamps.-The little incandescent lamps, 5,600 in number, which were strung everywhere, were manufactured by Swan, Maxim, Gérard, Edison, Weston, and Bernstein. Edison showed about 1,000, arranged spirally on a cylinder twenty feet high, some surrounded by white and others by colored bulbs, making a most beautiful effect. To the casual glance they are all much alike, having in common a filament of carbon bent in various shapes and clamped to leading wires, which are of platinum, as they pass through the glass bulb that incloses the filament, in which a high vacuum is produced. The point in which the incandescent lamps differ one from another is in the material composing the filament, and in its shape. This little filament has many enemies, the most formidable of which is called molecular carriage; that is, the carbon-particles are carried from the positive side of the loop to the negative, causing the filament to waste gradually until it breaks, and the lamp is destroyed. The various materials used in the different incandescent lamps are valuable in proportion to their power of resisting this molecular carriage. Edison, after a long series of experiments, decided in favor of a natural fiber, and, of all the hundreds of fibers that he tried, a certain species of bamboo found in China proved the best. The process by which the fibers are carbonized differs with each patentee. Edison cuts the strips of his bamboo four inches long by one eighth of an inch wide, by one sixty-fourth of an inch thick. This strip he bends in loop-shape around a mold. While it is carbonizing, he keeps it in place by weights that allow it to contract. Several of these loops are placed in a plumbago mold and exposed to intense heat for about four hours; when taken out, each carbon-loop is clamped to the leading wires and sealed in a glass bulb from which the air is exhausted. On the Swan lamp, used by the Brush Company in the United States, ordinary cotton-thread is employed, to which VOL. XXIV.-20 A

solidity is given by plunging it into sulphuric acid diluted with one third its volume of water. This "parchinentizes" the cellulose of the thread, making it homogeneous. The prepared thread, bent into a horseshoe-shape with a spiral in the middle, is carbonized by placing it in carbon-dust and raising to orange heat. The lamp is completed by inclosing the loop in a transparent glass globe in which a vacuum is produced. This lamp gives sixteen to twenty candle-power (an ordinary kerosene-burner gives five to six candle-power). The electrical resistance of this lamp is about forty ohms, while Edison's is 140.

Hiram S. Maxim's lamp has the general features of those described above, except that the filament used is stamped from a flat sheet of paper, in the shape of a letter M, and carbonized between sheets of thin paper in iron molds, and afterward treated to render it as homogeneous as possible, which is effected by heating the filament to incandescence in a carbonaceous atmosphere. The gas is decomposed by the heat of the incandescent filament, on which the liberated carbon is deposited. The thinnest parts become most heated and decompose the greatest amount of gas, and consequently receive the heaviest deposit. This tends to build up the carbon evenly, which is the great object in making the filament.

The incandescent lamps covered by the Weston patents were exhibited in great profusion at the exposition. The carbon of these lamps has a zigzag shape, and is made from cellulose by a process not yet made public. The resulting material is, before carbonizing, a translucent, elastic substance, and produces an exceedingly strong, metallic-looking carbon, capable of resisting very high temperatures for a long time. The Weston Company also exhibited an incandescent lamp of one hundred candle-power. It did not differ from their regular lamp in any particular, except that it was of a larger size, the loop being about six inches long.

The Bernstein lamp also appeared among the exhibits. The carbons of this lamp are tubular and bent into the form of a loop. They are made by carbonizing a finely woven cotton or silk fabric. The Gérard lamp's filament consisted of two fine carbon rods having the leading wires cemented to one end of each rod. The two other ends are cemented together. This is burned in a vacuum and looks like the letter V, when the lamp is hanging downward. A miniature lamp for dental and surgical operations was exhibited. This is only half an inch long, and has a carbon-loop of paper.

The currents used for incandescent lamps are usually of lower electro-motive force than are used in the arc-lamp. The lamps in all systems are connected in multiple arc, and any number can be burned on one circuit. About twenty-four incandescent lamps were fed by the Brush storage-battery. Each gave a steady, soft light of about fourteen candle-power.

Dynamos.-Numerous dynamos were exhibit