is fastened and the photographer waits until the kites become steady. When the kites are in motion the cord or wire has a tremor or pulsation which can easily be felt by a pressure of the finger on the cord. The photographer waits until this is no longer perceptible, when he jerks the thread and the picture is taken.

The advantage of scientific kite flying for making signals in warfare, also for taking pictures of fortifications can be appreciated. Already the United States. government has decided to utilize kites in connection with its signal service in the West, and the probabilities are that they will also be used at sea, as they can be readily sent up from the decks of vessels, with signals attached which can be seen a long distance, as will be noted by the accompanying photographs.

Just before the elections a string of kites with a banner bearing the names of candidates may be seen at a height of 1,000 or more feet over New York City. One of these was photo-.

graphed from the top of one of the tall buildings. A number of advertising streamers from fifteen to twenty-five feet in length are being sent up almost daily and such is the power of the kites carrying them that they remain elevated until hauled down at dusk. Several times during patriotic celebrations in New York, Mr. Horsman has sent up sets of kites carrying American flags, which appeared to be about two or three feet long when floating in the air, although in reality they were over twenty feet.

The aerial photographs which accompany this article were taken at Allenhurst, N. J. One shows the beach with the ocean breaking upon it, also a vessel in the distance, as well as one of the pleasure pavilions and walks and drives. Another is an enlargement of a photograph taken at the same resort, showing summer cottages, flower beds, as well as several cyclists and vehicles. This view was taken at an elevation of about three hundred feet.

O the average person the expending of $2,800,000 for a bridge would seem a risky investment. To him it would scarcely seem that such an enor

mous sum could possibly be realized in anything like a reasonable period of time from a mere bridge. Nevertheless such was the cost of the new railroad bridge across the Mississippi river at Thebes, Illinois, one hundred and thirty miles south of St. Louis; and it may be unhesitatingly said that not a shadow of doubt is entertained by its builders that the bridge will prove a paying investment. In fact, they had arrived at the certainty of its paying before the plans for its construction were complete; and it is probable that by their figures one

could learn just how many years will be required for the direct and indirect receipts of this bridge to balance its total cost and the compound interest thereon.

The Thebes bridge, as it is commonly called, forms an important link between several leading railway systems, and offers valuable aid to rapid transportation between large areas on each side of the Mississippi river. It forms a connection between the Illinois Central, the Chicago & Eastern Illinois and the St. Louis Southwestern railroads on the Illinois side, with the Frisco system, the Iron Mountain and the St. Louis Southern railroads on the Missouri side.

Before the completion of this bridge it was necessary for heavily loaded trains to pass either up the river to St. Louis or down it to Memphis or resort to the

old ferry system to cross. This last was always of limited capacity and subject to the embarrassments of the seasons of flood and ice. Hence traffic from certain points midway between these two old outlets and corresponding points on the other side of the river was often delayed for several hours, which, especially in regard to perishable freight, was a matter of serious consideration.

In addition to its value to commerce the Thebes bridge is of interest as affording a conspicuous model of perfection in bridge construction. It is one of the largest bridges in the United States, and with respect to the length of its center span but one bridge in this country and two abroad stand as its rivals. The entire length of the bridge, including its approaches, is four and seven-tenths miles. The steel superstructure is 2,750 feet long, the concrete viaducts combined are 815 feet long, and the remainder of the bridge's length is made up of graded earth approaches. The superstructure, which is divided into five spans, has a channel span 671 feet in length, an intermediate span on each side of 521 feet 2 inches, and shore spans of 518 feet 6 inches.

The total weight of the steel in the superstructure is 26,880,000 pounds. The free spans weigh 11,560 pounds per lineal foot, the suspended spans 7,720 pounds per lineal foot, and the cantilever arms 11,650 pounds per lineal foot. Supporting this huge mass of steel there are six piers of ashlar masonry with foundations on solid rock, and five of which have pneumatic caisson footings. The distance from the bottom of the lowest foundation to the top of the highest point of the superstructure is 231 feet.

Leading from the river's banks to the steel superstructure on each side there are concrete viaducts, built with arches. On the Illinois side there are five 65-foot arches and on the Missouri side six 65-foot and one 100-foot arches. These viaducts are built of the best Portland cement, and it is estimated that they contain 35,000 cubic yards. The bridge has a double track and the approaches are ballasted and laid with 85-pound rails. Of the $2,800,000 expended on the bridge, $1,400,000 went for the steel superstructure, $600,000 for its piers and foundations, $300,000 for the concrete arch viaducts, and the remaining $500,000 for the earth approaches.

used on high speed internal combustion. or gas engines. This resulted in diagrams that were distorted and of little value.

To overcome this fault, instruments called the manograph were brought out in Europe, where they are now used in the testing plants of automobile factories and by high-speed gas engine builders. Several of the instruments have been brought to America during the past year and are attracting the attention of tech

CARPENTIER,

the

nical men interested in the subject of internal combustion motors. One of these instruments, seen on the tripod in the photograph, Fig. 1, is built in Paris, and is known as the Hospitalier-Carpentier; other, suspended from the wall bracket, in Fig. 2, is made in AlsaceLorraine and is called the Schulze. Both are named after the designers and builders. The Carpentier is a portable instrument set on a stout tripod, while the Schulze is intended to be more permanently secured directly to the engine or to a rigid bracket near by. In both the principle of operation is much the

same.

Great ingenuity was displayed by the designers in avoiding the features of the steam engine indicator that rendered it unsuitable for engines running at speeds above 1,000 revolutions per minute. Instead of a system of levers moving

a long reciprocating arm carrying a pencil or needle, and a reciprocating drum supporting the card, the diagram is traced by a beam of light having no weight, which is caused to move by the oscillation of a tiny mirror about the size and weight of a dime. A plain wood box is fitted at one side with a brass tube supporting a diaphragm through which is admitted to the box a ray of light from a small electric arc lamp or an acetylene gas burner supported at the end of the tube. Immediately inside the box is a prism that refracts the beam of light upon the little mirror mounted in an aperture at the right hand end of the box. Here the rays are concentrated on the slightly convex mirror and reflected as a minute point of brilliant light upon a ground glass mounted in a removable slide in the left end of the box.

The most ingenious features of the instrument are the means adopted for moving this point of light on the ground glass to trace a diagram by oscillating the mirror and also the method of timing the movements of the point of light to coincide with the stroke of the engine piston. The mirror is supported at the back against three points, forming a right-angled triangle: The point at the apex of the angle is stationary, but the two others are the ends of movable pins. Springs press the mirror against the pins and keep the pins retracted. The longer pin is in contact at its other end with the center of a flexible diaphragm. The chamber in which the diaphragm is mounted is connected by a pipe with the cylinder of the engine. Pressure in the cylinder causes the diaphragm to bulge slightly and force the pin forward. This

in turn pushes the lower edge of the mirror inward, causing the point of light on the ground glass to move upward a distance exactly proportionate to the amount of pressure against the diaphragm. As the pressure varies the light. point rises and falls.

Side movement of the ray of light is effected when actuated by the smaller pin. Movements of this pin correspond with movements of the engine piston and the light on the ground glass moves from side to side always the same distance. When the instrument is fully connected with the engine and the engine is run, the light spot has both a lateral and a vertical motion, the one indicating the movement of the piston and the other the varying pressures in the cylinder. If the instrument is so connected with the en