range on good roads is about 40 miles for a truck and 75 to 100 miles for pleasure cars on one battery charge. Vehicle batteries are generally carried in hard rubber jars and are nearly always of the sealed type on account of the liability of splashing the electrolyte when the car is operated over ordinary highways. The cells are grouped in trays for easy handling, and all connections and couplings, terminals and battery straps are of unusually rugged design.

The present tendency in lead-battery design seems to be toward the use of more thin plates, as fifteen are furnished as a standard equipment more often than a smaller number. Such an equipment will give 180 ampere-hours, and in some types may develop fully 200 ampere-hours. The reasons for the increasing adoption of the thin-plate lead battery are, first, an augmenting demand for more speed and greater range of action per charge, and secondly, a realization on the battery-maker's part that the life of a thin plate is equal to that of the heavier ones if the installation is properly made. One standard jar size now being produced will work with from 11 to 15 plates. The high-ribbed type of jar is used, having at least three inches below the bottom of the plates for sediment space, this reducing the amount of washing and necessary cleaning out of the cells. The jars are assembled side to side in trays, with the plate surfaces set at right angles to the direction of car movement. One row of cells is mounted in each tray, these being set lengthwise in the battery compartment. This arrangement is said to reduce jar breakage.

Isolated Lighting Plants.—Many makers of storage batteries have developed types for use in residence and factory lighting where central station power is not available. The advantages of electricity for the supply of light, heat and power have led to a demand for the satisfactory and economical operation of isolated plants. The marvelous development of the internal combustion gas, gasoline or kerosene engine and the improvements in the various forms of lamps have created an active interest in the application of the storage battery to isolated plants of moderate size, it now being recognized where uninterrupted twenty-four-hour service is desired a storage battery is an absolute necessity. Usu

ally in isolated plants the engine and generator capacity is sufficient for the total number of lamps connected, although they are all seldom in use at one time, consequently the plant operates at but partial load during the total lighting hours. This means low efficiency, poor regulation and high fuel costs. The installation of a storage battery corrects this weakness by permitting the operation of the generator at the full or the most economical load for

a few hours and then shutting down entirely, the battery providing the current for the balance of the time.

In many cases it can be so arranged that the generator need be operated only every second or third day, and then at the most. convenient time. No additional labor is required; in fact, this cost is usually lessened, while the fuel cost and maintenance and repair expense are much reduced. By taking current directly from the battery, steady lights are obtained and the noises of engine at night avoided. When on special occasions unusual lighting is required, the battery may be discharged in parallel with generator, and demands equal to the combined capacity of battery and