of the piston, and it is practically impossible to connect the instrument “in time" with the concealed piston, special mechanism is provided for synchronizing the instrument with the engine.

Mechanical connection with the shaft is effected by inserting a tapered plug in a concentric hole bored in the end of the crankshaft and threaded, and then forcing upon the plug a correspondingly tapered socket in the end of a flexible shaft connected at its other end to the instrument. The flexible shaft rotates one of a pair of planetary gears mounted on a brass disc, one concentric with it and actuating the pin that moves the mirror through a link and lever. By means of a thumb nut the brass disc can be rotated and carries the little eccentric driving gear around the driven gear, thus changing the "time" of the pin with relation to that of the engine piston. Connection with the engine shaft is, therefore, made at random and the instrument synchronized with it by this planetary

mechanism. Motion of the point of light on the ground glass has to be watched in order to adjust the instrument properly. Its movements are very erratic until synchronism is secured, when the lines traced on the glass during compression and expansion will coincide if the engine is turned over by outside effort or is allowed to run by momentum during several revolutions. When they are made to coincide the instrument is ready to take "cards."

So rapid is the movement of the spot of light that when the engine is running at 1,000 revolutions or more, the eye no longer sees a single spot of light, but the retina retains the image so long that the continuous line of a complete diagram is seen. By observing this the gas engine expert can note every change in pressure throughout the cycle of operations due to changes in time of ignition, in gas mixture, in radiation, and so on. It reveals to him instantly nearly everything that goes on inside the cylinder. Permanent records can be taken at any time by substituting a photographic dry plate for the ground glass and securing a negative. Perfect records can be secured at speeds of more than 2,000 revolutions per minute.

Not only is the manograph adapted to use with gas engines, but is equally useful in connection with steam engines, air compressors and vacuum pumps. By means of diaphragms of different thicknesses, each calibrated and accompanied by a ruled paper scale upon which the negative can be laid, the pounds of pressure at every point of the piston stroke can be determined, and the power developed can be calculated.

Although the principle of the Schulze manograph is the same as that of the Carpentier, the construction differs somewhat. A Nernst incandescent lamp projects the light upon the mirror through a long tube at the base of the instrument. The instrument is connected directly to the two-to-one shaft of the engine through the medium of small bevel gears and rods. The Schulze manograph is made also in quadruple form for taking diagrams simultaneously from the four cylinders of the usual automobile engine.

T has been a difficult matter to adapt the automobile to use on the farm owing to the fact that it has been hard to secure the necessary traction of the wheels on the ground. Ribbed wheels do not have the necessary gripping effect unless they are held down by enormous weight, and even then the resistance of the load is often sufficient to cause the tractor wheels to simply gouge out the ground as they revolve, without moving ahead.

These difficulties have been overcome in a new machine known as the Farmobile. The system of propulsion consists in employing an inert wire cable which lies upon the ground and extends across the field, the ends of the cable being secured.

The car is equipped with a pair of

drums which are operated by a four cylinder gasoline engine. The car stands over the cable, and the cable passes with a few turns over the drum so that as the drum revolves it winds along the cable and draws the car at a proportionate speed. At each end of the car is a tension device comprising a pair of positively driven rolls between which the cable passes, the rolls pressing against the cable keeping the cable taut between the tension devices and the drums so that the cable cannot loosen its coil on the drums.

As the cable has several coils on both drums, and the coils cannot possibly slip, and as the drums are positively driven, it will be readily seen that in operation the car is bound to travel and pull its load, and the load may be as great as the engine has power to pull.

In use, the cable takes care of itself and

shifts itself to accommodate the path in which the machine is steered. Each end of the cable is fastened to a pulley, and the pulley rides along a cable arranged transversely to the propelling cable. The machine is provided with a steering wheel which controls the angular position of the front wheels similarly to an automobile.

When a machine is steered so that it rides along the propelling cable in a line at right angles to the end cable, the pulley lies still on the end cable; but when the machine is steered to the right or left, for example, to avoid obstruction, the machine will draw the propelling cable into an angle with the end cable whereupon the pulley naturally rolls along, carrying its end of the main cable to a point directly opposite the machine. In traveling back and forth across the field, the cable is shifted in this manner. This shifting action does not actually occur until the machine has approached somewhat close to the pulley, for when there is a long amount of the main cable on the tension side, the weight of the cable and friction of moving it sideways on the ground prevents such movement.

At all times, however, a short amount of cable immediately in front of the ma

chine always swings to the right or left when necessary to suit the steering of the machine.

The machine is equipped with gearing for reversing the drums to propel the machine backward along the cable, but the steering is difficult in such method of backward travel and in use the machine is turned around at each end of the field so that it travels forward each time it traverses the field. To accommodate this, and to obviate the necessity of disengaging the cable from the drums, or of swinging the whole cable end for end, the main cable near each end has a section which is separable from the cable and forms a detachable link.

The machine when at either end of the main cable stands over the separable section or link, the latter then being wound around the drums and extending at each end somewhat beyond the machine. Then by unhooking both ends of the short section from the main cable, the machine is turned around taking the section with it, and the section thus reversed by the machine is hooked into position again in the main cable, whereupon the machine can proceed forward. The machine may be driven by its own wheels.

Powerful Petrol-Motor THE accompanying illustration shows

one of the largest petrol-motors yet constructed for industrial use. This motor, which is developing 140 brake horse-power at 420 revolutions, is to be applied to drive electric generators for providing current to motor operating passenger coaches. The cylinders, six in number, are placed horizontally and are arranged opposite to each other, with a six-throw crank-shaft in the center. They have a diameter of nine inches each, by a stroke of ten inches. The liners and jackets are of iron, and were cast separately. The joints are metal to metal; and the liners are held in position by studs. The combustion-chambers are also of cast iron and are water-jacketed. The jacket for the walls of the cylinders is independent of that for the combustion heads, so that a water joint with the combustion space is avoided.

The engine is started with the assistance of cartridges, and special arrangement of breech-mechanism is supplied. The cartridge, of ordinåry sporting size, contains a charge of 280 to 300 grains of black powder-sufficient to give the piston a pressure of about

one-half the ordinary working pressure. These cartridges are fired by special mechanism, which is worked in conjunction with the timing gear for the usual electric ignition. The total petrol consumption of the motor during a nonstop run of three hours is thirty-three gallons.

Such machines merely indicate the strides that have been made in mechanics during the past few years, and give but a hint of future develop

ment.

Artificial Stone ARTIFICIAL stone for building pur

poses has become a most important industrial item, and several very successful methods of producing it have been perfected. A most notable forward step, however, was recently made in England, where blast-furnace slag is now being utilized in the manufacture of stone-like substances. By slight modifications in the process, all kinds of marble are produced, and a signal success has been achieved in the manufacture of artificial lithographic stone, which experts have declared to be superior to some of the best samples of the natural material.

In using blast-furnace slag for the manufacture of artificial stone, it is broken up in an ordinary stone crusher and the ground to a powder. This powder is then mixed with quicklime, seven parts of slag-powder to one part of lime, the two ingredients being thoroughly amalgamated in a revolving mixer. Water is then introduced to such an extent that the whole mass is reduced to a pasty mass. duced to a pasty mass. This material is then placed in metal molds, in which it is squeezed until almost all the water has

THE LEVAVASSEUR HYDROPLANE.

been forced out, and the resulting blocks are of the consistency of chalk These blocks are next thoroughly dried, and placed in heavy iron cylinders from which the air is exhausted. When a complete vacuum is attained, carbonic acid gas is allowed to enter the cylinders, permeating the blocks for a period of three days. At the end of the three days the hydrate of lime has become recarbonated and binds the mass into what is to all practical purposes best building stone.

By substituting limestone or dolomite for slag, it is possible to prepare a mixture, the method of mixing being as when slag is used, in which 34 to 7% consists of calcium hydrate, or a mixture of calcium and magnesium hydrates, obtained by calcining the stone. When this mixture

COUNT DE LAMBERT'S HYDROPLANE.

is impregnated with carbonic acid gas, the lime and magnesium are converted into carbonates, the blocks being consolidated and converted into stone. When manufacturing artificial marble and lithographic stone, coloring matter is added to the paste before it is introduced into the moids. The finished stone to all appearances is the same as natural marble, and will take the same degree of polish. Whether its weather resisting qualities are the same can, of course, only be determined by time, but it is asserted that these properties are the same as those of the natural stone.

There is also in operation in England

Novel Motor Crafts THE several craft here shown illustrate the latest development in swift-going motor boats. The de Lambert hydroplane, constructed by Count de Lambert, is built after the manner of the catamarans of Australasia and the West Indies.

The basis consists of five planes, each of which measures some four feet by ten. The total area of support is, therefore, about two hundred square feet. With the exception of the front plane, the planes are set at an angle of five per cent. The incline of the front plane is slightly greater. This craft is propelled by a fifty horse power eight-cylinder motor. The other photographs here reproduced represent the Levavasseur freak boat, the Antoinette, which is built in two parts.