containing the daily gas supply as derived from a transportable gas bottle at a maximum pressure of two atmospheres; the metal conduit connected, both with the filling valve and with the gas bottle; the manometer for observing the increase in

Apart from its use for the lighting and heating of houses Blau gas allows of a number of additional applications. It is generally known that oxy-hydrogen flames have been lately used with excellent results in many branches of industry for what is known as autogenous welding. In fact, a blower supplying hydrogen as fuel and pure oxygen in the place of air will raise most materials to melting temperature, the remarkable intensity of this flame being accounted for by the absence of diluting nitrogen. Experience has further shown all gases containing as elementary components hydrogen and carbon, to be susceptible of giving equally satisfactory results. Blau gas in its liquefied condition, therefore, is as convenient for this purpose as compressed hydrogen and even cheaper than acetylene which has likewise been used with good results.

Another use of Blau gas is for high-speed soldering. The relatively high temperature required for a number of technical processes can hardly be obtained by means of ordinary Bunsen burners. In order to increase the effects of the latter, a special blower has therefore been used

WHAT necessity is the mother of invention is nowhere truer than in conjunction with the development of trackless trolley cars in Europe during the last three or four years. So predominant is the esthetic in many of the municipal corporations of old Austria and parts of Germany that the citizens have refused trolley corporations the right to disfigure their attractive streets by laying a trolley track through them; and yet these same citizens have demanded up-to-date methods of transportation and the result has been a premium on certain methods of locomotion which would give all the advantages of the electric trolley car without the two or four steel rails as well as the pathway of ties needed to support them.

The earliest solution of the problem was in the adoption of electric buses which carried their own storage batteries capable of forty miles of travel. Batteries commensurate for the work weighed approximately one ton and often more, and these batteries being very delicate constructions the jolting of the roads and streets rapidly deteriorated them and frequent renewals of the positive plates were necessary. This renewal problem invariably confronted the promoter, and to it was added the extra wear and tear on the vehicle because of having to carry around that ton of battery which served as its life blood. This ton load was frequently in excess of the passenger load carried and as such greatly reduced the mileage life of the solid rubber tires, reduced the possible speed and made it impossible to show an expected or even operating profit.

Other promoters turned to the gasoline motor bus which is now the accepted convenience in metropolitan cen

ters such as London, Paris, Berlin, and is making its inroads into New York. and other American cities. Experience has shown that the gasoline bus only shows a profit where the promoter has a number in operation, a complete system in fact, so that he can establish his own repair department, own his own garage and in some cases rebuild his own machines. Where a promoter operates one, two or three vehicles the experiment has invariably proved a signal failure.

Confronted with this dual situation and with that modern Macedonian cry coming from numerous towns and cities of Europe, "Give us the equal of the trolley but without its tracks," continental inventors devoted much study to the problem. Honors have rested on several but to Ludwig Stoll belongs much credit for the solution of the trackless trolley problem as well as to one German motor car manufacturer who assisted Stoll in translating into the practical his conceptions of what the system should be. The Mercedes-Stoll system, the result of this brains-factory alliance, is now in every-day use in Vienna, in Germany, and is being introduced in England. Its cost of operation is such as to make it a practical system and the cost of maintenance is low. The system calls for but a couple of overhead electric wires, one for the current from the power house to the motor on the vehicle and the other a return wire to complete the electric circuit.

In one of the illustrations is shown a double trolley system operating near Vienna, Austria, showing two trackless trolleys approaching near the curb and giving due share to a couple of farm wagons_traveling in the opposite direc

tion.

Each trolley requires two overhead wires over which runs a fourwheel truck that takes the place of the pulley which travels beneath the wire in

the American trolley system. This truck through its four grooved wheels, two riding on the positive wire and two on the negative wire, is pulled along through a cable connecting with the car at the right front or immediately in front of the driver. Hanging direct from the truck is a large ball, designated the pendulum, which holds the truck on the two wires, and close to this ball is a large loop in the cable running to the car which loop is taken up when the car has to turn off to the side of the road to pass other vehicles. This loop would only permit of the car deviating ten or twelve feet from beneath the overhead wires.

Flexibility, of course, is the life blood of the trackless trolley permitting as it does of operating on any city thoroughfare, no matter how congested, without in any wise hampering the other vehicles. on the street and further permits of the trackless trolley turning to the right or left of other slow-moving vehicles and so making faster time than is often possible with the trolley car in crowded streets.

In small towns or through rural districts where the expense of having four overhead wires, two for cars traveling in one direction and two for those in the opposite direction, is too great, the Mercedes-Stoll system permits of the use of but two wires, as shown in the second illustration. The two wires serve for vehicles traveling oppositely but when they meet the trucks cannot pass on the two overhead wires and the cables from the car to the truck on one car are exchanged with those on the other, this exchange being facilitated by having a socket union in the cable. In this respect the trackless trolley with one set

of overhead wires is greatly superior to the single-track trolley cars whereon cars traveling in opposite direction have to wait at switches until they pass. The trackless trolley is also a switchless trolley. Should the faster of two vehicles. moving in the same direction want to get ahead of the slower this exchange of cables will suffice without occasioning a delay of more than a few seconds.

The various trackless-trolley systems operating in parts of Austria afford good scope for ascertaining the enduring qualities of these machines. In one system, near Vienna, the road is two and a half miles long and five cars with a carrying capacity of twenty-one passengers each are used. Each car makes approximately one hundred miles per day. This is a two-wire line and only ten seconds are lost due to exchanging cables when cars meet. Each car is propelled by two twenty two twenty horse-power motors, one carried on each of the rear road wheels. These motors are capable of an overload of one hundred per cent, which makes the negotiating of ten per cent grades with full load of passengers an easy matter. The cost of running these cabs is from seven to ten cents per mile. One of the records shows one car operating in Austria to have carried 45,000 passengers and over 1,000 packages without one cent of repairs. The electric motors have gone for sixteen successive months without any repairs. It is this low cost of maintenance that augurs so favorable for the trackless trolley car. The car with but a couple of electric motors is simple as compared with the gasoline bus; and it is free from the delicate storage battery which is greatly reduced in usefulness if the vehicle operates over rough roads.