se-power sizes, the largest being a four-cylinder engine. All
three sizes were constructed to run at 1,200 revolutions per minute. In
this make the cylinders were secured to the crank case by means of
four long tie bolts passing through bridge pieces arranged across the
cylinder heads, thus relieving the cylinder walls of all longitudinal
explosion stresses. These bridge pieces were formed from chrome
vanadium steel and milled to an 'H' section, and the bearings for the
valve-tappet were forged solid with them. Special attention was given
to the machining of the interiors of the cylinders and the combustion
heads, with the result that the exceptionally high compression of 95
lbs. per square inch was obtained, giving a very flexible engine. The
cylinder heads were completely water-jacketed, and copper water-jackets
were also fitted round the cylinders. The mechanically operated valves
were actuated by specially shaped cams, and were so arranged that only
two cams were required for the set of eight valves. The inlet valves at
both ends of the engine were connected by a single feed-pipe to which
the carburettor was attached, the induction piping being arranged above
the engine in an easily accessible position. Auxiliary air ports were
provided in the cylinder walls so that the pistons overran them at the
end of their stroke. A single vertical shaft running in ball-bearings
operated the valves and water circulating pump, being driven by spiral
gearing from the crankshaft at half speed. In addition to the excellent
balance obtained with this engine, the makers claimed with justice that
the number of working parts was reduced to an absolute minimum.

In the two-cylinder Darracq, the steel cylinders were machined from
solid, and auxiliary exhaust ports, overrun by the piston at the inner
end of its stroke, were provided in the cylinder walls, consisting of a
circular row of drilled holes--this arrangement was subsequently adopted
on some of the Darracq racing car engines. The water jackets were of
copper, soldered to the cylinder walls; both the inlet and exhaust
valves were located in the cylinder heads, being operated by rockers and
push-rods actuated by cams on the halftime shaft driven from one end
of the crankshaft. Ignition was by means of a high-tension magneto,
and long induction pipes connected the-ends of the cylinders to the
carburettor, the latter being placed underneath the engine. Lubrication
was effected by spray