Chapter VII: MISCELLANEOUS.--The Xylophone.--2 engravings. 7793 (2)

With respect to canalized rivers, the difficulty that must always have existed when these rivers (as was mostly the case) were provided with weirs to dam up the water for giving power to mills has been augmented of late years by the change in the character of floods. It has frequently been suggested that in these days of steam motors in lieu of water power, and of railways in lieu of water carriage, the injury done by obstructing the delivery of floods is by no means compensated by the otherwise all but costless power obtained, or by the preservation of a mode of transport competing with railways. It has thereupon been suggested that it would be in the interests of the community to purchase and extinguish both the manufacturing and the navigating rights, so as to enable the weirs to be removed, and free course to be provided for floods. It need hardly be said, however, that if means could be devised for giving full effect to the river channels for flood purposes, while maintaining them for the provision of motive power and of navigation, it is desirable that this should be done. The great step in this direction appears to be the employment of readily or, it may be, of automatically movable weirs. Two very interesting papers on this subject by Messrs. Vernon-Harcourt and E. B. Buckley were read and discussed in the session 1879-1880. These dealt, I fear exclusively, with foreign, notably with French and Indian, examples. I say I fear, not in the way of imputing blame to the authors for not having noticed English weirs, but because the absence of such notice amounts to a confession of backwardness in the adoption of remedial measures on English rivers. An instance, however, of improvement since then has been the construction by Mr. Wiswall, the engineer to the Bridgewater Navigation Company (on the Mersey and Irwell section of that navigation), of the movable Throstle Nest weir at Manchester. It does seem to me that by the adoption of movable weirs, rivers in ordinary times may be dammed up to retain sufficient water to admit of a paying navigation and water for the mills on their banks; while in time of flood they shall allow channels as efficient for relief as if every weir had been swept away.

But the great feature of late years in canal engineering is not the preservation or improvement of the ordinary internal canal, but the provision of canals, such as the completed Suez canal, the Panama canal in course of construction, the contemplated Isthmus of Corinth canal--all for saving circuitous journeys in passing from one sea to another; or in the case nearer home of the Manchester ship canal, for taking ocean steamers many miles inland.

But the old fight between the canal engineer and the railway engineer, or, more properly speaking, between the engineer when he had his canal "stop" on and the same individual when he has his railway "stop"--you will see that I am borrowing a figure, either from Dombey & Son, where Mr. Feeder, B.A., is shown to us with his Herodotus "stop" on, or, as is more likely, I am thinking of the organs to be exhibited in the Second division, "Music," of that exhibition of which I have the honor to be chairman--I am afraid this is a long parenthesis breaking the continuity of my observations, which related to the old rivalry between canal and railway engineering. I was about to say that this rivalry was revived, even in the case of the transporting of ocean vessels from sea to sea, for we know that our distinguished member, Mr. Eads, is proposing to connect the Atlantic and Pacific oceans by means of a ship railway across the Isthmus of Panama. He suggests that the largest vessels should be raised out of the water, in the manner commonly employed in floating docks, and should then be transferred to a truck-like cradle on wheels, fitted with hydraulic bearing blocks (this being, however, not a new proposition as applied to graving docks), so as to obtain practical equality of support for the ship, notwithstanding slight irregularities in the roadway, while he proposes to deal with the question of changes of direction by the avoidance of curves and by the substitution of angles, having at the point of junction of the two sides turntables on which the cradle and ship will be drawn; these can be moved with perfect ease, notwithstanding the heavy load, because the turntable will be floating in water carried in circular tanks.

The question of preserving the level of the turntable, whether unloaded, partially loaded, or loaded, is happily met by an arrangement of water ballast and pumping. I cannot pass away from the mention of Mr. Eads' work without just reminding you of the successful manner in which he has dealt with the mouth of the Mississippi, by which he has caused that river to scour and maintain a channel 30 feet deep at low water, instead of that 8 feet deep which prevailed there before his skillful treatment. Neither can I refrain from mentioning the successful labors of our friend Sir Charles Hartley, in improving the navigation of that great European river, the Danube. I am sure we are all rejoiced to see that one of the lectures of the forthcoming series, that on "Inland Navigation," is to be delivered by him, and I do earnestly trust he will remember it is his duty to the Institution not to leave important and successful works unreferred to because those works happen to be his own.

I regret that time does not admit of my noticing the many improved machines for excavating, to be used either below water or on dry land. I also regret, for similar reasons, I must omit all mention of ship construction, whether for the purpose of commerce or of war, a subject that would naturally follow that of rivers and of ship railways and canals, and would have enabled me to speak of the great debt this branch of civil engineering owes to the labors of our late member, William Froude, and would have enabled me also to deal with the question of material for ships, and with the question of armor plating, in which, and in the construction of ordnance, our past president, Mr. Barlow, and myself, as the two lay members of the Ordnance Committee, are so specially interested.

MILITARY ENGINEERING APPLIANCES.

The mention of armor plates inevitably brings to our minds the consideration of ordnance, but I do not intend to say even a few words on this head of invention and improvement--a topic to which a whole evening might well be devoted--because only three years ago my talented predecessor in this chair, Sir William Armstrong, made it the subject of his inaugural address, and dealt with it in so masterly and exhaustive a style as to render it absolutely impossible for me to usefully add anything to his remarks. I cannot, however, leave this branch of the subject without mentioning, not a piece of ordnance, but a small arm, invented since the date of Sir William's address. I mean the Maxim machine gun. This is not only one of the latest, but is certainly one of the most ingenious pieces of mechanism that has been devised. The single barrel fires the Martini-Henry ammunition; the cartridges are placed in loops upon a belt, and when this belt is introduced to the gun, and some five or six cartridges have been drawn in by as many reciprocations of a handle, the gun is ready to commence firing. After the first shot, which must be fired by the pulling of a trigger in the ordinary way, the gun will automatically continue to send out shot after shot, until the whole of the cartridges on the belt are exhausted; and if care is taken before this happens to link on to the tail of the first belt the head of a second one, and another belt to this, and so on, the firing will be automatically continuous, and at a rate anywhere between one shot per minute and six hundred shots per minute, dependent on the will of the person in charge of the gun, the whole of the operations of loading, firing, and ejecting the cartridge being performed by the energy of the recoil. This perfectly automatic action enables the man who works the gun to devote his whole attention to directing it, and as it is carried on a pivot and can be elevated and depressed, he can, while the gun is firing, aim the bullets to any point he may choose.

Since 1862 the power of defending seaports has been added to by the application of submarine mines, arranged to be fired by impact alone, or to be fired on impact when (under electrical control) the firing arrangement is set for the purpose, or to be fired electrically from the shore by two persons stationed on cross-bearings, both of whom must concur in the act of explosion. These mines are charged with gun-cotton, the development of which owes so much to Sir Frederick Abel, while for purposes of attack the same material, not yet in practical use for shells, is taken as the charge for torpedoes, which are either affixed to a spar or are carried in the head of a submerged cigar-shaped body. By a compressed air or by a direct steam impulse arrangement these weapons are started on their course and are directed, and then the running is taken up by their own engines operating on screw propellers, driven by a magazine of compressed air contained in the body of the torpedo. Means are also provided to maintain the designed level below the water surface. The torpedo may either be projected from the war ship itself or from one of those launches which owe their origin to our member, Mr. John Isaac Thornycroft, who first demonstrated the feasibility of that which was previously considered to be impossible, viz., the obtaining a speed of twenty miles and over from a vessel not more than 80 feet long. Experiments have been carried on in the United States by Captain Ericsson to dispense with the internal machinery of the torpedo, and to rely for its traverse through the water upon the original impulse given to it by a breech-loading gun, carried at the requisite depth below the water level in a torpedo boat. This gun, having a feeble charge of powder at a low gravimetric density, fires the torpedo, and, it is said, succeeds in sending it many yards, and with a sufficient terminal velocity to explode the charge by impact. Also, in the United States, experiments have been made with a compressed air gun of 40 feet in length and 4 inches in diameter (probably by this time replaced by a gun of 8 inches in diameter), to propel a dart through the air, in the front of which dart there is a metallic chamber containing dynamite. Although no doubt the best engineer is the man who does good work with bad materials, yet I presume we should not recommend any member of our profession to select unsuitable materials with the object of showing how skillfully he can employ them. On the contrary, an engineer shows his ability by the choice of those materials which are the very best for his purpose, having regard, however, to the relative facilities of carriage, to the power of supply in sufficiently large quantities, to the ease with which they can be worked up or built in, and to the cost.

USES OF CEMENT.

Probably few materials have been found more generally useful to the civil engineer, in works which are not of metal, than has been Portland cement. It should be noticed that during the last twenty-two years great improvements have been made in the grinding and in the quality of the cement. These have been largely due to the labors in England of our member, Mr. John Grant, to the labors of foreign engineers following in his footsteps, and to the zeal and intelligence with which the manufacturers have followed up the question, from a scientific as well as from a practical point of view, not resting until they were able with certainty to produce a cement such as the engineer needed. I do not know that there is very much to be said in the way of progress (so far as the finished results are concerned) in the materials which Portland cement and other mortars are intended to unite. Clean gravel and ballast and clean sand are, I presume, very much the same in the year 1884 as they were not only in the year 1862, but as they were in the year 1. The same remark applies to stone and to all other natural building materials; and, indeed, even the artificial material brick cannot in these days be said to surpass in quality the bricks used by the Romans in this island nineteen hundred years ago, but as regards the mode of manufacture and the materials employed there is progress to be noted. The brick-making machine and the Hoffmann kiln have economized labor and fuel, while attempts have been made, which I trust may prove successful, for utilizing the clay which is to be found in the form of slate in those enormous mounds of waste which disfigure the landscape in the neighborhood of slate quarries. Certain artificial stones, moreover, appear at last to be made with a uniformity and a power of endurance, and in respect of these qualities compare favorably with the best natural stone, and still more favorably having regard to the fact that they can be made of the desired dimensions and shape, thus being ready for use without labor of preparation.

PRESERVATION OF WOOD.

Reverting to natural materials, there remains to be mentioned that great class, timber. In new countries the engineer is commonly glad to avail himself of this material to an extent which among us is unknown. For here, day by day, owing to the ready adaptability of metals to the uses of the engineer, the employment of wood is decreasing. Far, indeed, are we from the practice of not more than a hundred years ago, when it was not thought improper to make the shell of a steam engine boiler of wooden staves. The engineer of to-day, in a country like England, refrains from using wood. He cannot cast it into form, he cannot weld it. Glue (even if marine) would hardly be looked upon as an efficient substitute for a sound weld; and the fact is, that it is practically impossible to lay hold of timber when employed for tensile purposes so as to obtain anything approaching to the full tensile strength. If it be desired to utilize metals for such a purpose, they can be swollen out into appropriate "eyes" to receive the needed connection; but this cannot be done with wood, for the only way of making an enlarged eye in wood is by taking a piece that is big enough to form the eye, and then cutting away the superfluous portion of the body. Moreover, when too much exposed to the weather, and when too much covered up, wood has an evil habit of rotting, compared with the rapidity of which mode of decay the oxidizing of metals is unimportant. Further, one's daily experience of the way in which a housemaid prepares a fire for lighting is suggestive of the undesirability of the introduction of resinous sticks of timber, even although they may be large sticks, into our buildings. Many attempts, as we know, have been made to render timber proof against these two great defects of rapid decay and of ready combustibility, and, as it appears to me, it is in these directions alone one can look for progress in connection with timber. With respect to the first, it was only at the last meeting of the Institution we presented a Telford medal and a Telford premium to Mr. S. B. Boulton for his paper "On the Antiseptic Treatment of Timber," to which I desire to refer all those who seek information on this point. With respect to the preservation from fire of inflammable building materials, the processes, more or less successful, that have been tried are so numerous that I cannot even pretend to enumerate them. I will, however, just mention one, the asbestos paint, because it is used to coat the wooden structures of the Inventions Exhibition. To the employment of this, I think, it is not too much to say those buildings owed their escape, in last year's very dry summer, from being consumed by a fire that broke out in an exhibitor's stand, destroying every object on that stand, but happily not setting the painted woodwork on fire, although it was charred below the surface. I do not pretend to say that a surface application can enable wood to resist the effects of a continued exposure to fire, but it does appear that it can prevent its ready ignition.

(_To be continued._)

* * * * *

THE CATHEDRAL OF THE INCARNATION.

The Cathedral of the Incarnation, at Garden City, N. Y., the memorial of Mrs. Cornelia M. Stewart to her husband, Alexander T. Stewart, was opened April 9, 1885, by impressive religious ceremonies. At precisely 11 o'clock the chimes in the cathedral tower rang out a clear and resonant peal, and the people thronged into the building through its tower and transept entrances.

The effort has been made to reproduce in the cathedral a pure type of the Gothic architecture of the thirteenth century, without its ruder and less refined characteristics. The strained and coarse images designed to illustrate "the world, the flesh, and the devil," which seem so strange and unapt to American visitors to the great Continental cathedrals, are almost entirely omitted in this reproduction. The carving, too, in deference to the more sensitive tastes and better skill of this age, is far more artistic and natural than in the old originals. Flowers in stone are made to resemble flowers, and heads are fashioned after a human pattern, and clusters of figures are modeled in a congruous and modern manner. But aside from changes of this kind, the new and magnificent edifice upon Hempstead Plains is a perfect example of the elaborate and picturesque Gothic structures of mediæval days.

It is built of brown sandstone raised in colossal blocks. The spire, floriated richly and graduated with a precise symmetry, rises to an extreme altitude of 220 feet 6 inches. The extreme length is about 170 ft. The massive oaken front doors are carved handsomely, and contain the arms of the Stewart family, the Clinch family (Mrs. Stewart's maiden name), the Hilton family, and those of Bishop Littlejohn, the Episcopal head of the Long Island Diocese. The porch or tower entrance, which is the main entrance to the building, is paved with white marble. In the center of the floor the Stewart arms are enameled in brass, showing a shield with a white and blue check, supported by the figures of a wild Briton and a lion. The crest is a pelican feeding its young, and the motto is "_Prudentia et Constantia_." These heraldic figures are made a special feature of the main aisle. Directly in the center of the auditorium floor the Stewart and Clinch arms are impaled, enameled in brass. On the floor in the choir the Hilton arms are placed. They bear the patriotic motto "_Ubi libertas ibi patria_," with a deer for a crest. The floor of the ante-chancel presents the arms of the diocese. Its insular character is especially prominent. The shield of barry wavy contains three crosslets, the peculiar sign of the cathedral. It is supported by dolphins. The crest is a ship, and under all is the sacred motto, "I will set his dominion in the sea." The workmanship of all these arms is superb.

By far the most wonderful works of art in the edifice are the windows of stained glass and the musical facilities. Every window presents a theme suggestive of the Incarnation. The windows of the porch present several of the Old Testament characters and events which prefigured the birth of Christ, and over the door leading to the nave are figures of Adam and Eve and of Abraham and Sarah. The four windows on the south side of the nave show the Annunciation, the dream of Joseph, the salutation of Elizabeth, and the refusal of the stable to the parents of the infant Redeemer. In the first window of the transept is presented the inn-keeper's refusal of refuge to Joseph and Mary. The great window of the south transept, in all about thirty feet high, one of the largest windows in the world, shows the family of Jesse, the ancestor of Jesus. Jesse is resting at full length; above him is King David, and all around are figures of his descendants leading up to the Virgin Mary with the Holy Child in her arms. Above all, in the apex of the windows, are the emblems used in prophecies of Christ's coming. The third window of the south transept shows the Nativity, with the Babe in the manger. Two windows in the choir are chosen with special reference to the regular service of the church. The first represents the appearance of the star in the east to the shepherds of Bethlehem, introducing the "Gloria in Excelsis," and the second shows the presentation of Christ in the temple, suggesting the "Nunc Dimittis," the "Magnificat," and the "Benedictus." Then beautiful representations are given in the north transept windows of the Magi bringing gifts to the infant Saviour, and the wise men before King Herod. The windows of the nave show the flight into Egypt, the massacre of the innocents, and the return to Nazareth.

The north window of the transept is the most magnificent of all. It presents Christ in glory, thus suggesting the "Te Deum." Jesus sits enthroned with the angels and archangels, prophets, apostles and martyrs of the church in all ages bending in adoration before Him, while the heavenly choir are waving palms and chanting music in honor of Heaven's King. The smaller windows under the roof show the hierarchy of heaven indicating by music and dances the joy of the celestial world at the scenes of the Incarnation depicted below. Upon a bright, sunny day the cathedral is made exquisitely beautiful by the mellowed radiance of these windows. They were designed and manufactured by Clayton & Bell, of London, and are esteemed to present the perfection of their work. Their colors, rich and varied, blend in perfect harmony, and the intricacy of the groupings makes each one as interesting as an oil painting.

Six different organs have been built in different parts of the building. The most important of these is the great organ in the north apse. It is furnished with four keyboards and 124 stops, with twenty-four combination stops that admit of more than a million combinations of sound. On either side of the choir is another organ, with a fourth of great power in the crypt, a fifth in the tower, and an echo organ built under the vaulting of the roof. This produces a soft and weird music. All the organs are operated from the keyboard of the great apse organ, which also plays the chimes of thirteen bells in the tower. The choir instruments are made to correspond by means of iron tubes filled with wind by a bellows engine in the crypt of the apse. A second engine in the crypt of the tower operates the bellows that inflate the instruments in the crypt, the tower, and the vaulting. All the organs and the chimes are connected by electric wires, about twenty-six miles of which are employed, supplied with electricity by a motor in the tower engine room. Sublime and grand are the only terms which can suggest the effect of the volume of harmony produced by these instruments in united action. They were made by Hilborne L. Roosevelt, of this city.

The ante-chancel contains the bishop's throne, the dean's seat, and the stalls of the clergy and canons, all of carved mahogany. A superb work of art is the altar, in the chancel, which is separated from the ante-chancel by a heavy bronze railing. The altar is of statuary marble manufactured by Cox & Sons, of London. Its corner columns are of black marble, supported by others of flecked marble, with panels of Sienna and Griote. Between the panels are rich carvings, done in Antwerp, representing the temptation and fall in Eden; Abraham's offering of his son Isaac; Moses raising the brazen serpent in the wilderness; the annunciation to the Virgin; the birth scene in the stable; the Crucifixion and the Resurrection. The slab of the altar is inlaid with five crosslets, representing the five wounds, and the symbol "I. H. S."

None of the cathedral windows are richer than those which circle the chancel. They present Christ as the Good Shepherd and the apostolic college. An excellent piece of chiseling is done by Sibbel, the sculptor of this city, in the panels over the credence. They are figures of the high priest with a slain lamb, the type of the bloody sacrifice, and Christ with sheaves of wheat and clusters of grapes, the unbloody sacrifice. Beneath them is the text, "Thou art a prophet forever after the order of Melchisedec." The chancel is paved with red and yellow Sienna marble as center pieces, flanked with squares of red Griote and white marble, the whole bordered with strips of red and black marble. The ante-chancel is paved with blocks of red Griote and verd antique. Two magnificent pieces of statuary stand on either side of the transept. The first represents Religion holding a little model of the cathedral. The other is an image of Hope. They were done by Park, the Florentine sculptor.

In the south apse is the baptistery, built with a tower furnished with chimes. Its supporting columns are of Languedoc marble clustered with smaller ones of Sienna and verd antique. Six columns support the dome. Each is of a different marble, crowned with sculptured capitals in high relief. The windows are appropriate in theme. They represent Noah with the ark; the building of the ark; Moses holding the tables of the law; the passage of the Red Sea; John the Baptist; the Baptism of the eunuch; St. Philip, the deacon; and the Baptism of Christ. In the center of the room stands the font upon an octagonal base of two steps. Its pedestal and bowl are traced with symbolic carvings. Over it is a canopy of elaborately carved mahogany drawn into a spire bearing a gold crown, studded with rubies and amethysts.

At the foot of the chancel is the pulpit, of bronze, designed by Sibbel. Its base is surrounded by figures representing hearers of the Word. Mr. Sibbel has incorporated an anachronism in one of these figures that will be exceedingly interesting in coming years. It shows the features of Henry G. Harrison, of this city, the architect of the cathedral. The lectern stands on the other side of the ante-chancel, representing Christ blessing little children. Superb bronze columns with brass coronas of natural flowers support the roof of the building. The triforium is carved in the richest style with passion flowers, fuchsias, roses, and lilies.

In the crypt below are the robing rooms of the clergy and the choir and the Sunday-school room. Its windows show the arms of every American diocese. Beneath the choir is the chantry, furnished in carved oak. Adjoining this room is the famous mausoleum erected to the memory of Alexander T. Stewart. It is constructed of statuary marble, and consists of fourteen bays, at the angles of which are triple columns of the most richly colored imported marbles arched above the elegantly carved capitals, with open tracery, through which the headlights of the colored glass are seen. The subjects of the thirteen windows relate to the passion, death, resurrection, and subsequent appearances of Christ, and are executed in admirable design and color. They were made by Heaton, Butler & Bayne, of London. Above the window openings rises a dome-shaped ceiling, in carved marble, with a pendent canopy in the center. The pavement, of black and white marbles, radiates from the center of the sides of this polygonal structure, and a large white urn, delicately draped after Sibbel's designs, stands under the pendent canopy. It bears Mr. Stewart's name. The two entrances to the mausoleum are guarded by open-work bronze gates of elegant design and workmanship.--_N. Y. Tribune._

* * * * *

MOVABLE MARKET BUILDINGS.

The furnishing of food supplies has always been a question of great importance to cities, and there are few of the latter, great or small, where the establishment of markets is not the order of the day.

At Paris especially, by reason of the massing of the population, which is annually increasing, the multiplicity of the wants to be satisfied renders the solution of this question more and more difficult. The old markets, some of the types of which still exist in various parts of Paris, were built of masonry and wood. They were massive structures into which the air and light penetrated with difficulty, and which consequently formed a dangerous focus of infection for those who occupied them, and for the inhabitants of the neighboring houses. So the introduction of iron into the construction of markets will bring about a genuine revolution whose influence will soon make itself felt in all branches of the builder's art.

The Central Markets were to have been built of masonry, and the work had even been begun, when, under the pressure of public opinion, the architect, Mr. Baltard, was led to use iron. Evidently, the metal that permits of covering vast spaces with the use of distant bearing points that present a small surface in plan, and leaves between them wide openings that the sun and air can enter in quantity, was the only thing that was capable of giving the solution sought. So it has been said, and rightly, that the Central Markets are, as regards the distribution and rational use of materials, the most beautiful of the structures of modern Paris. This system of construction at once met with great success, and the old markets are everywhere gradually disappearing, in order to give place to the new style of buildings.

Notwithstanding their number, the Parisian markets long ago became insufficient, and wants increased with such rapidity that it became impossible to supply them. The municipal administration was therefore obliged, especially in populous quarters, to tolerate perambulating peddlers, who carried their wares in hand carts. This system has the drawback that it interferes considerably with travel, and especially in streets where the latter is most active. Moreover, the merchants and their goods are exposed to the inclemency of the weather. In other places, where large spaces were utilizable, such as squares and avenues, very light structures, that could be easily put together and taken apart, were erected, and markets were opened in these once or twice a week. This method presents serious advantages. Iron markets, in fact, despite the immense progress that they mark, present disadvantages that are inherent to all stationary structures. It is necessary to erect them in populous centers, where land is consequently of great value; and the structure itself is costly.

The result is that the prime cost is very great, and this forces the city to charge the merchants high rents, and the consumer has to pay for it. With movable markets, on the contrary, the city can utilize large areas of unproductive ground, and find new resources, although renting the stalls at a minimum price. The expense connected with the structure itself is very small. In fact, the distinguishing character of such structures is their portability--so that the same shed can be used in any number of different places.

The principal expense, then, will be for carriage; but it is easy to see that there will always be an economy in their use. This is a fact, moreover, that practice has verified, for it is well known that Paris does not get her expenses back from her stationary markets, while the movable ones yield a revenue.

On another hand, as stationary markets are costly, it results that they cannot be multiplied as much as necessary, and so a portion of the inhabitants are daily submitted to a loss of time in reaching the one nearest them.

Finally, from a hygienic standpoint, movable markets present a very great advantage over stationary ones. The latter, in fact, notwithstanding their large open spaces, never get rid of the vitiated air that they contain, and the bad odors that emanate from them are also a source of annoyance and danger to the neighborhood. In movable ones, on the contrary, when the structure is taken apart, the air, sun, and rain disperse all bad odors, and the place is rendered wholesome in an instant.

We have now demonstrated what great advantages the city of Paris and her population might derive from the establishing of movable markets.

It is easy to see that well established structures of this kind would render great services in small towns also. They might entirely replace stationary iron markets, the high cost of which often causes municipalities to preserve their old, inconvenient, and unhealthy structures. As a general thing, market is held but once or twice a week in small towns. In the interior the structure could be taken apart, and the place rendered free.

The question, then, is to have a system of construction that shall satisfy the different parts of the programme that we have just laid out, that is to say, strength, lightness, rapidity of erection, and ease of carriage. The shelters that are at present employed for movable markets at Paris are very primitive, and are wanting in solidity and convenience. They consist simply of wooden uprights to which are affixed cross-pieces that support an impermeable canvas.

In order to render it possible to extend the system of movable markets, it became necessary to first find and study the proper material.

During the year 1883 the city of Paris resolved to make some experiments, and the Direction of Municipal Affairs commissioned Mr. Andre, director of the Neuilly works, to submit to him a plan for a structure that could be easily taken apart. The plan finally proposed seemed to meet all the requirements of the case, and a group of ten structures was erected. The trial that was made of these proved entirely satisfactory. The city then made concession to the Neuilly company, for six years, of the market in Boulevard Richard-Lenoir, of those of La Reine Park, and of the Madeleine flower markets. A six months' trial has shown the great resistance of the materials that we are about to describe in detail.

The structure is supported by cylindrical hollow iron uprights that are firmly connected with the ground as follows: At the places where they are to be fixed, small catches are inserted in the ground so that their upper surface comes flush therewith. These catches consist of two cast iron sides bolted together, and of a bottom and ends formed of flat iron--the end pieces being bent so as to form cramp irons. Each of the sides is provided internally with a projecting piece, and an inclined plane as a wedge. In case the catch becomes filled with dirt, it can be easily cleaned out with a scraper. The iron upright terminates in a malleable cast iron shoe, which is screwed on to it, and which is provided beneath with a projection in the form of a reversed T, the upper part of the horizontal branches of which is beveled off in a direction opposite that of the inclined planes of the catch. This projection enters through the slit and fits into the two wedges, and a simple blow of a hammer suffices to make the adherence perfect.

The front and hind uprights differ only in length, and the roof timbers are joined at their upper extremities. The figures so well show how the parts are fitted together as to render an explanation unnecessary.

The dimensions of these structures vary from 6.5 to 5.75 feet in length by 6.5 in width and 6 in height. The rafters are prolonged so as to project 4.25 feet in front, in order to form a protection for the purchaser. This part of the rafters, as well as the longitudinals, is supported by three curved iron braces, which are put in place as follows: The timbers are provided with a ring fixed by a screw, and one extremity of the brace is inserted into this, while the other is held against the upright by a sliding iron socket. The longitudinal timbers are supported between each two uprights by an iron rod that rests upon a block of stone fixed in the ground.

The front ends of the rafters are connected by a longitudinal, 18 feet in length.

The structure is covered with waterproof canvas held in place by wooden rods, to which it is attached.

The wood employed is pitch pine.

An entire market of 300 stalls can be put up in three hours by one workman and four assistants.--_Le Genie Civil._

FIG. 1.--GENERAL VIEW OF A MOVABLE MARKET.
FIG. 2.--SHOES.
FIG. 3.--MODE OF JOINING THE ROOF TIMBERS.
FIG. 4.--IRON SUPPORT.
FIG. 5.--SECTION OF A SHOE INSERTED IN THE CATCH.
FIG. 6.--CATCHES.
FIG. 7.--WATERPROOF CANVAS.]

* * * * *

DINOCRATES' PROJECT.

Vitruvius relates that the architect Dinocrates proposed to Alexander the Great to carve Mount Athos in such a way as to give it the shape of a man, whose one hand should support an entire city, and whose other should carry a cup which received all the waters from the mountain, and from which they overflowed into the sea.

Alexander, charmed with the idea, asked him if this city was to be surrounded by land capable of supplying it with the grain necessary for its subsistence. Having ascertained that the provisioning could only be done by sea, Alexander said: "Dinocrates, I grant the beauty of your project; it pleases me, but I think that any one who should take it into his head to establish a colony in the place you propose would run the risk of being taxed with want of foresight; for, just as a child can neither feed nor develop without the milk of a nurse, so a city cannot increase without fertile fields, have a large population without plenty of food, and allow its inhabitants to subsist without rich harvests; so, while giving the originality of your plan my approval, I have to say to you that I disapprove of the place that you have selected for putting it into execution. But I want you to stay near me, because I shall have need of your services."

This gigantic project had doubtless been suggested to the Macedonian architect by the singular forms that certain mountains affect. It is not rare, in fact, to see human profiles delineated upon the sky, and this phenomenon especially happens in countries where the folded limestone strata have been broken up in such a way as to give rise to deep valleys perpendicular to the direction of the chain. If we look at these folds from below in an oblique direction, we shall see them superposed upon one another in such a way as to represent figures that recall a human profile.

In the seventeenth century, Father Kircher conceived the idea of taking up Dinocrates' plan upon a small scale, and composed the landscape shown in Fig. 1. The drawing remained engraved for a long time upon a marble tablet set into the wall of Cardinal Montalte's garden at Rome. Later on, artists improved and varied this project, as shown in Figs. 2 and 3. By looking at these cuts from the sides of the page, it will be seen that they form human profiles. Fig. 2 represents an old woman, and Fig. 3 a man whose beard and hair are formed by shrubbery.

We do not think that these conceptions have ever been realized, although Heron in his treatise on Dioptra, and Father Scott in his Parastatic Magic, have described instruments that permit of making the necessary outlines to cause grounds to present a given aspect from a given point. These instruments consist essentially of a vertical transparent frame upon which is drawn a vertical projection of the landscape that it is desired to obtain.

* * * * *

In the island of Goa, near Bombay, there is a singular vegetable called "the sorrowful tree," because it only flourishes in the night. At sunset no flowers are to be seen, and yet after half an hour it is full of them. They yield a sweet smell, but the sun no sooner begins to shine upon them than some of them fall off, and others close up; and thus it continues flowering in the night during the whole year.

* * * * *

THE CRUTO INCANDESCENT LAMP.

An electrical exhibition on a comparatively small scale was opened in Paris, March 22, 1885, with considerable eclat, the President of the Republic being present. Engines to the extent of 200 H.P. are employed to work the lights. Among the exhibits is the Cruto light. _Engineering_ says: At the first glance it presents the same appearance as an Edison lamp, having the same form of globe, and apparently a similar luminous filament. But this latter is made in an entirely different manner. A platinum wire is employed, 1/100 of a millimeter in diameter. This is obtained by the Wollaston process, that is to say, a piece of coarse platinum wire is covered with a stout coating of silver, and drawn down till the outside diameter is 1/10 millimeter. The silver coating is then dissolved in a bath of nitric acid, and the platinum wire is left behind. This wire is then cut into lengths, bent into a U form, and placed in a glass globe, in which circulates a current of bicarbonated hydrogen obtained by the action of sulphuric acid on alcohol. This gas, previously purified, circulates around the platinum filament, through which an electric current is passed sufficient to bring it to a red heat. This decomposes the gas, and a thin coating of absolutely pure carbon is deposited on the wire. The operation is continued until a sufficient thickness of carbon has been deposited for each type of lamp, and the method of regulating the amount of deposit is effected very simply, and, in fact, almost automatically. Indeed, one of the most interesting features of the process is its great simplicity, although it is somewhat more costly than the ordinary methods of producing incandescence lamps. After having been subjected to the action of the gas for two or three hours, the filament is taken from the glass globe, its diameter is carefully measured, the length is calibrated, and it is set on a platinum support, to which it is soldered by a very ingenious process. The filament is then introduced into a second glass globe charged with bicarbonate of hydrogen; it is placed between pincers that hold the carbon near its union with the platinum, and the platinum some millimeters below. These pincers are then thrown into circuit, and a powerful current is passed through the part which is to be soldered. The platinum and carbon become incandescent, the bicarbonate is decomposed, and a fresh deposit of carbon solders the filament to its support. The system thus mounted is placed within the permanent globe, and a vacuum is obtained in the ordinary way, while the testing and finishing details present nothing of special interest. The finished lamp is then photometrically tested, and placed on a support something like the Edison mounting. Upon it are engraved the working constants. As an ordinary practical result, these lamps, working with 50 volts and 1.15 amperes, give a luminous intensity of 20 candles, or the equivalent in luminous spherical intensity of 1.1 Edison A lamps. This result is interesting, especially as the life of the lamp ranges from 900 to 1,100 hours, as was demonstrated by various careful tests made with some 250 lamps; the most valuable trials having taken place at the Turin Exhibition. After prolonged use, a diminution in the fall of potential is produced, to a more marked degree than in the Edison lamp, and the light can be maintained constant by increasing the strength of the current in a proportion that can be determined by means of resistances. The Cruto filament examined under the microscope appears to be uniformly magnetic, and is very regular, except at the curved parts where the diameter is slightly diminished, and it is here that rupture generally takes place. The great structural regularity of the filament probably accounts for its high durability, and from the fact that it may be worked with a higher current than probably any other form of incandescence lamp. M. Desroziers in a series of experiments obtained as much as 250 carcel spherical luminous value per horse-power; this characteristic is one likely to be of great value in electric lighting by incandescence of high intensity. At present only 20-candle lamps are made on the Cruto system. The carbon filament, when properly prepared, is gray in hue and of metallic appearance; it is built up in very fine laminæ indicating the mode of manufacture. The results obtained with these lamps vary as much as 25 per cent., according to the care bestowed in producing the filament. If traces of air exist in the globe, they very quickly manifest themselves by the surface of the glass becoming blackened, while an increased energy is required to maintain the brightness of the light.

In the early days of this lamp it was thought necessary to remove the delicate platinum wire which forms the core of the filament, by raising the strength of the current sufficiently to destroy it in the course of manufacture. This, however, was given up, and the platinum now remains either as a continuous wire or as a series of small separated granules.

* * * * *

ELECTRIC LIGHT APPARATUS FOR MILITARY PURPOSES.

In the first period of the siege of a stronghold it is of very great importance for the besieged to embarrass the first progress of the attack, in order to complete their own armament, and to perform certain operations which are of absolute necessity for the safety of the place, but which are only then possible. In order to retard the completion of the first parallel, and the opening of the fire, it is necessary to try to discover the location of such parallel, as well as that of the artillery, and to ply them with projectiles. But, on their side, the besiegers will do all in their power to hide their works, and those that they are unable to begin behind natural coverts they will execute at night. It will be seen from this how important it is for the besieged to possess at this stage of events an effective means of lighting up the external country. Later on, such means will be of utility to them in the night-firing of long-range rifled guns, as well as for preventing surprises, and also for illuminating the breach and the ditches at the time of an assault, and the entire field of battle at the time of a sortie.

On a campaign it will prove none the less useful to be provided with movable apparatus that follow the army. A few years ago. Lieut. A. Cuvelier, in a very remarkable article in the _Revue Militaire Belge_, pointed out the large number of night operations of the war of 1877, and predicted the frequent use of such apparatus in future wars.

The accompanying engraving represents a very fine electric light apparatus, especially designed for military use in mountainous countries. It consists of a two-wheeled carriage, drawn by one horse and carrying all the apparatus necessary for illuminating the works of the enemy. The machine consists of the following parts: (1) A field boiler. (2) A Gramme electric machine, type M, actuated directly by a Brotherhood 3-cylinder motor. (3) A Mangin projector, 12 inches in diameter, suspended for carriage from a movable support. This latter, when the place is reached where the apparatus is to operate, may be removed from the carriage and placed on the ground at a distance of about a hundred yards from the machine, and be connected therewith by a conductor. Col. Mangin's projector consists of a glass mirror with double curvature, silvered upon its convex face. It possesses so remarkable optical properties that it has been adopted by nearly all powers. The fascicle of light that it emits has a perfect concentration. In front of the projector there are two doors. The first of these, which is plane and simple, is used when it is desired to give the fascicle all the concentration possible; the other, which consists of cylindrical lenses, spreads the fascicle horizontally, so as to make it cover a wider space.

The range of the concentrated fascicle is about 86,000 feet. The projector may be pointed in all directions, so as to bring it to bear in succession upon all the points that it is desired to illuminate. The 12-inch projector is the smallest size made for this purpose. The constructors, Messrs. Sautter, Lemonnier & Co., are making more powerful ones, up to 36 inches in diameter, with a corresponding increase in the size of the electric machines, motors, and boilers.

The various powers make use of these apparatus for the defense of fortresses and coasts, for campaign service, etc.

The various parts of the apparatus can be easily taken apart and loaded upon the backs of mules. The only really heavy piece is the boiler, which weighs about 990 pounds.

* * * * *

ELECTRICITY AND MAGNETISM.[1]

[Footnote 1: Introductory to the course of Lectures on Physics at
Washington University, St. Louis, Missouri--_Kansas City
Review._]

Prof. FRANCIS E. NIPHER.

It was known six hundred years before Christ that when amber is rubbed it acquires the power of attracting light bodies. The Greek name for amber, _elektron_, was afterward applied to the phenomenon. It was also known to the ancients that a certain kind of iron ore, first found at Magnesia, in Asia Minor, had the property of attracting iron. This phenomenon was called magnetism. This is the history of electricity and magnetism for two thousand years, during which these facts stood alone, like isolated mountain peaks, with summits touched and made visible by the morning sun, while the region surrounding and connecting them lay hidden and unexplored.

In fact, it is only in more recent times that men could be found possessing the necessary mental qualities to insure success in physical investigation. Some of the ancients were acute observers, and made valuable observations in descriptive natural history. They also observed and described phenomena which they saw around them, although often in vague and mystical terms.

They, however, were greatly lacking in power to discriminate between the possible and the absurd, and so old wives' tales, acute speculations, and truthful observations are strangely jumbled together. With rare exceptions they did not contrive new conditions to bring about phenomena which Nature did not spontaneously exhibit--they did not experiment. They attempted to solve the universe in their heads, and made little progress.

In mediæval times intellectual men were busy in trying to set each other right, and in disputing and arguing with those who believed themselves to be right. It was an era of intellectual pugilism, and nothing was done in physics. In fact, this frame of mind is incompatible with any marked success in scientific work.

The physical investigator cannot take up his work in the spirit of controversy; for the phenomena and laws of Nature will not argue with him. He must come as a learner, and the true man of science is content to learn, is content to lay his results before his fellows, and is willing to profit by their criticisms. In so far as he permits himself to assume the mental attitude of one who defends a position, in so far does he reveal a grave disqualification for the most useful scientific work. Scientific truth needs no man's defense, but our individual statements of what we believe to be truth frequently need criticism. It is hardly necessary to remark, also, that critics are of various degrees of excellence, and it seems that those in whom the habit of criticism has become chronic are of comparatively little service to the world.