at its ends on the slide blocks is calculated to add greatly to the friction and resistance. Unlike their usual practice, the air and exhaust valves are placed on the end of the combustion chamber, one side shaft actuating the whole of the valves, and the gas inlet of both cylinders is under the control of one centrifugal governor.

The self-starter used by this firm is very simple and efficient.

Fielding & Platt, Gloucester

Messrs. Fielding & Platt's experiments in gas motors date back to 1879, from which year to 1890 they were engaged, like many other firms, in comparing other types with the now universal Otto.' The evolution of their present form of valves has been very interesting. However, a description of these is outside the scope of this treatise. It is difficult to understand why, when designing an engine to combine the many advantages of the girder frame, engineers should nullify those advantages by arranging the bearings so that the force of the explosion has to be taken up by the cap bolts, when it is as easy to arrange that the main casting shall be utilised for the purpose. Fig. 39 shows that this firm, like others, have fallen into this error, as in the 100 B.H.P. engine this defect is very pronounced. The girders and main bearings are in one casting, to which the cylinder is bolted, the bolts for which are, however, covered over with a loose ring. Although this gives the engine a very neat appearance, it does not admit of easy access to the bolts. The air and exhaust valves are carried in one box, forming part of the combustion chamber, the air valve being arranged at the top and the exhaust valve at the bottom. The governor and gear are of the ordinary dead-weight centrifugal pattern.

An illustration of the development of large power in gas engines is shown in figs. 40 and 41, wherein 180 B.H.P. is arranged to drive direct an air compressor at the high speed of 150 revolutions per minute. The distinctive feature is that the crank shaft, arranged between the back end of one cylinder and the front end of the other, is placed above the centre

line of the cylinder, to allow the rods coupling the two pistons to travel in a direct line under the crank shaft, one connecting

rod serving the purpose of the two cylinders. The cycle of operations is the same as that shown in fig. 2 at B, and fig. 4

E

FIG. 39.-100 B.H.P. FIELDING ENGINE

that is, an impulse is obtained at every revolution when working at full power.

The compressor, which was constructed by Messrs. Johnson & Co., Stratford, London, is a two-stage one, compressing the air up to 40 lbs. per square inch above the atmosphere.

FIG. 42.-1 H.P. NOM. FIELDING VERTICAL ENGINE

The engine is fitted with a Fielding high-pressure starter applied to one cylinder only. The makers state that a highly satisfactory test has been made with this plant, using producer gas, although the results were not sufficiently accurate for publication.