than the chemical disintegration of the batteries and therefore high efficiency can be maintained for almost an indefinite length of time. The only parts likely to give trouble are the circuit breaker points and distributor segments, which should be cleaned from time to time with smooth sandpaper or, if the points are badly pitted, they should be filed square. Spark plugs invariably give the most trouble and in the event of skipping which is confined to some of the cylinders, spark plugs will probably be found at fault.

In this general summary of engine troubles, the symptoms have been given in most cases, but it was not necessary to give remedies, for in nearly every instance after considering the trouble and its cause the remedy is self-evident, therefore there is little reason to offer for a lot of suggestions which are at once realized.

It must not be supposed that all the trouble likely to be encountered in operating an internal combustion motor has received consideration. Quite to the contrary, for regardless of the make of engine or how conversant the operator may be, there are little difficulties which arise from time to time which may not have been considered in this paper, but what I desire to lay particular stress on is this-if the several suggestions offered in this article are learned, I don't mean word for word for that is of no value, but a general understanding of the foregoing methods, so that an operator realizes that there is no hidden mystery entering the operation of a gas engine, every complication-no matter how seemingly intricate -is at once recognized by a certain symptom or symptoms and a specific remedy applied.

In nearly every locality where gas engines are called upon to furnish power for various purposes, there are to be found "gas engine experts," who, in many instances, depend upon a living through mistakes made by others-the owners of gas engines. This condition of affairs would scon become a thing of the past if many owners and prospective owners of gas engines would realize the extreme simplicity and entire dependability of the modern gas engine and in the event of a trouble, irrespective of how seemingly complicated, calmly consider the symptoms and bring about a remedy themselves, and in a surprisingly short time the problems which formerly necessitated calling outside assistance would become a source of interesting research.

Tritt Electric Company of Union City, Indiana, has just brought out a new catalog describing a new battery charger for automobiles and motor boats. This battery charger, which they have given the trade name of TECO, is of the permanent magnet type of generator from which current may be taken for ignition as well as lighting. It is provided with an automatic, electric cut-out so that when the current in the dynamo builds up sufficiently it opens the cut-out

This country is not the only one in which tractor cultivation of the soil is being investigated. A consular report states that on April 15 of this year an International Motor Plowing Contest was held near the city of Tunis in French Africa. There were represented at this affair seventeen different makes of apparatus of which nine were gasoline and oil tractors. Of these nine, seven were American, one English and one Italian. The American tractors carried away all the prizes in their respective classes. It is believed that several hundred tractors can be disposed of in that market within the next ten years. Tunisia is a land of large estates and the home of an important class of progressive and wealthy colonists who are interested in modern farming methods and machinery.

The connecting rods of gas engines are now invariably made of forged steel. Usually a fairly high carbon, open hearth steel is selected having a carbon content of about forty points. Where a stronger rod is desired nickel steel or vanadium steel is employed. The nickel steel contains about three per cent of nickel and the vanadium steel about one-quarter of a per cent of vanadium. Small as these quantities may appear to the layman, they are nevertheless enough to greatly increase both the tensile strength and the stiffness of steel.

The steel used for connecting rods is supplied in the form of billets by the steel mills according to whatever chemical specifications may be desired. These billets are then worked up into the proper size and shape in a forging press. The billets are first heated to a bright cherry red in a gas furnace, and then hammered into the right shape in a big power press that is fitted with the

FIG. 94. CONNECTING ROD WITH "H" SECTION. NOTE DIE CAST CRANK PIN BUSHINGS.

right shaped dies to produce the section of rod desired. This method of manufacturing produces a very dense, tough material and at a minimum cost since the expense of forging, once the dies are made, is very low.

In earlier days connecting rods were often roughly forged by hand with the aid, perhaps, of a steam hammer, and then finished on a planer or milling machine. Some were even made of cast iron and others were cast and then malleabelized. Rods made in this way were cheap but they were not reliable. The drop forged rods of the present day are singularly uniform in quality of material and rarely ever cause any trouble through breakage.

The only cast rod that is safe to use is made of phosphor bronze. This is said to be equal to steel but it is much more costly excepting where only a few engines of a certain size are made and then the cost of dies and forgings when spread over only a few pieces would make the cost high. There are a few gas engine builders

FIG. 95. ROUND SECTION CONNECTING ROD.

from three to five times the crank in larger engines.

The cross section of connecting rods varies from the simple circular section to those of rectangular or H section. Considering the weight of metal employed, the H section is stronger than any other form of rod, and since it can be forged as easily in the drop press as either a circular or a rectangular section, the saving in weight means a saving in cost. The only machine work done is at the ends. Some connecting rods having a body of circular section are turned and finished throughout, but this practice was much more prevalent in the past than it is at present. Nowadays the practice in all machine construction is to machine only those parts that require great accuracy or that bear against other surfaces. Plain black parts are easier to keep clean than polished metal and they are not liable to become rusted. Views of the principal gas engine connecting rods are shown in figures 94, 95 and 96, showing the H section, round section and rectangular section respectively.

The illustrations also show different methods

FIG. 96. CONNECTING ROD OF RECTANGULAR SECTION AND WEDGE ADJUSTMENT FOR WRIST PIN.

of forming connecting rod ends and of securing the bearings. The wrist pin end of steel rods, that is the end attached to the piston, should always be fitted with a bushing of some anti-friction metal, preferably bronze, though some suecess has been achieved with white metal. This