becoming the private carriage of the wealthier classes to be used on all occasions.
If the motor-car in the guise of a private carriage has developed at an astonishing rate, its adaptation to the needs of the community, as a public service vehicle, has been even more rapid. The first cabs placed on the streets of London in 1903 were by no means a success, but the cabs constructed by the French house of Renault and first introduced in London in 1906 rapidly effected a revolutionary change in the means of individual transport. Apart from the improved speed of the motor-cabs, they gained popularity because of the use, on each one of them, of the taximeter, showing at a glance the amount of the fare, thus preventing overcharge on the part of the driver. One effect of the employment of motor-cabs and motor-omnibuses has been to reduce slightly the total number of vehicles, and to quicken a large volume of the traffic; it is now being recognized that to increase the speed of the whole of the traffic of London by about 5 m. an hour is practically equivalent to doubling the width of the whole of the main streets.
The new British act of 1903, which was enacted for three years only, was, during the parliamentary session of 1906 and subsequent sessions, continued from year to year because of the difficulty that was experienced in reconciling conflicting views about the control of motor-cars. The 1903 act raised the speed limit to 20 m. per hour and gave the local government board power to close to motor traffic such roads as, on inquiry, might be deemed unsuited therefor, and to impose a speed limit of 10 m. an hour or less in dangerous places, such as narrow streets in a town or through a village. A few serious accidents in England, and many abroad, have kept alive the fear that the motor-car is a dangerous vehicle that should be restrained or held in check by stringent legislation. Thus from 1904 onwards, the motorist was under continuous police supervision. Police traps, or measured distances, over which the motor-car is timed by the police, were established in most of the counties of England, and, whilst, without a doubt, many real offenders were caught, it is equally true that many an innocent driver was unfairly accused, whilst motorists guilty merely of technical infringements of the law were summoned.
The attitude of the police in showing little or no leniency in the application of the law probably, however, did good in other directions, although these were not contemplated either by the law-givers or the police themselves. It considerably limited the use of excessively powerful cars (for example, a 60 or 90 h.p. car that could easily attain 60 m. an hour), and experience has demonstrated the fact that, intersected as England is with a network of narrow roads carrying considerable traffic, there is little opportunity for the full power of such a car to be used. The result has been that the comparatively low-powered vehicle has been developed in efficiency, bringing with it the advantages of economy in running, simplicity of mechanical details, cheapness of maintenance and ease of control and management.
The principle of the internal-combustion engine has not been altered since Daimler’s day, but the mechanical details of the engine have undergone constant revision and improvement, until in 1910 it was safe to say that a four-cylindered engine, with a cylinder bore of 4 in., constructed, we will presume, in 1899, might have developed 20 h.p. or less, Whereas engines of the same cylinder bore made in 1908 and 1909 actually developed 60 h.p. and more, and the attainment of even greater efficiency was in sight in 1910. Experience showed that the saving of weight meant greater economy in fuel and also in tires, the two principal items in the upkeep of the motor-car. Engine design has undergone unceasing improvement, and constructional methods have been continuously advanced, with the end in view of attaining lightness, not only in the moving parts, but in the inert parts. Lightness in reciprocating parts, such as the pistons, connecting rods and valves, has enormously improved crank-shaft speed. Cylinder castings are now made far lighter, whilst the water jacketing, for dissipating the excess of heat from the cylinder walls, is now of sufficiently ample proportions and, in consequence, better lubrication of the cylinder walls can be maintained. This again conduced to piston speed. The induction valves of engines of the earlier types were opened under atmospheric pressure, the reduced pressure in the cylinder, caused by the downward movement of the piston, enabling the pressure of the outer atmosphere to open the valve against its light spring, and to carry in a charge of the carburetted air that constituted the explosive mixture. But it was found that the automatic or atmospheric inlet valve opened late on the induction stroke and closed early, so that the engine only received an attenuated charge. One of the earliest improvements in engine design, therefore, was the employment of the mechanically-operated inlet valve operated by a cam exactly as the exhaust valve is operated. This valve could be fully opened as soon as the piston had begun its downward or induction stroke, and could be held open during the momentary period when the piston was at rest at the bottom of the stroke, thus ensuring a full charge of explosive mixture. The method of exploding the charge in the cylinder has undergone revolutionary changes. The first method, that of heating the exterior of a closed tube connected with the cylinder, quickly gave way. to electric ignition because it was found that the charges could not be exploded by the hot tube until the piston had reached the top of its stroke, and, at the comparatively high piston speed of these engines, the piston had moved some distance on its downward stroke before the exploded gas had begun to expand. Electric ignition was an improvement because it enabled a “lead” to be given to the explosion, a low voltage current (from four to six volts of about one ampere being sufficient for the purpose) being automatically switched on to the primary circuit of a coil, the induced current in the secondary circuit being of a voltage sufficiently high (calculated at from 5000 to 10,000 volts of a very small amperage) to jump across a, gap left in a sparking plug inserted in the cylinder. By rotating the body of the switch (called the contact breaker) the ignition could be timed to suit exactly the speed of the pistons and, in this way, greater piston speed was obtainable. The great development of this system was the introduction by Mr F. R. Simms, in conjunction with Herr Bosch, of the magneto machine, known as the Simms-Bosch magneto, the prototype for many such appliances. This machine, in its simplest elements, produces a low voltage current (assumed to be of about eight or ten volts) by the rotation of an armature in the magnetic field of a set of magnets, the rotation being effected through the timing-gear wheels of the engine. The low tension current is conveyed through a primary circuit inducing the secondary current which is employed for igniting the charges. The advantages of the magneto are, firstly, that the primary current is created by the engine, and that the need for an accumulator as a source of that current is avoided and, secondly, that the spark is more efficient because the faster the armature is revolved the more intense is the primary current and the induced current, consequently, the charge is ignited more rapidly. The magneto machine has almost entirely displaced the accumulator system for ordinary running, although, as the latter makes for easier starting, it is often fitted as an addition.
Great gain in power has been secured from improvements in the lubrication of the internal-combustion engine. It is now recognized that a small supply of oil to the journals and bearings of such an engine is insufficient, but in the early days it was found difficult to give the journals and bearings more oil without too much getting on to the cylinder walls, because the latter were lubricated by the oil that was thrown on to them by the spinning action of the webs of the crank-shaft and by the connecting-rod ends, these latter dipping into a well of oil in the lower part of the crank-case. The modern method has overcome this difficulty. The cranks and connecting-rod ends no longer dip into the oil, for the latter drains away into a sump or reservoir below the base of the crank chamber. Thence it is passed through a filter and pumped to ducts which convey the oil under pressure to the crank-shaft journals. Sometimes it is conducted thence along ducts bored in the crank-shaft and
