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114 The latest models of motor cycle have all the attributes of a well-designed motor car chassis, and some are best described as a car chassis on two wheels. The outstanding difference between a motor car and a motor cycle is that the latter is practically always fitted with an air cooled engine, i.e. an engine which radiates the heat generated by the explosions of gas in the cylinder directly from the cylinder to the atmosphere, instead of through the medium of water. Between the cylinders of most car engines and the atmosphere there is a jacket of water conducting the heat to a radiator, through which the water passes from top to bottom by natural circulation. There are instances of water-cooled bicycle engines and air-cooled car engines, but the cycle engine is normally air-cooled.

The motor bicycle represents the latest and most improved form of cycle extant, and the evolution of the cycle industry from its first introduction to this country, in 1868, to the present day has meant employment for thousands of workers and fortunes for many employers.

Whether the cyclist elects to provide the motive force by his own efforts or prefers to call in the aid of the internal combustion engine is a question of personal choice. The pedal bicycle, as it is termed, provides exercise with recreation, and the motor is therefore scorned by some athletic enthusiasts. The dependability and speed of the motor cycle are, however, now an established fact, and the advantages of the mechanical propulsion cannot be overlooked where time is a factor. On the other hand, the pedal bicycle is a restful and noiseless form of locomotion for those who do not care for the hurry and bustle of a motor cycle ride, and cycling, when undertaken in accordance with ones powers, is probably the most health giving form of recreation for the mind and body.