crankcase  comprises two crankshafts  and  arranged parallel
to one another, one with a long-stroke crank , the other with
a short-stroke crank ; the two cylinders  and , provided
respectively with pistons  and  and connecting rods  and
, are respectively arranged above one of the two crankshafts
 and .
The crank of the short-stroke crankshaft 
coacts with the connecting rod  of the piston  in the smaller
cylinder  and the crank of long-stroke crankshaft  coacts
with the connecting rod  of the piston  in the larger cylinder
The two cylinders  and  are connected
one by one, from one row to the other, through a recess in the cylinder
head , so as to form a pair of cylinders  and  in communication
with each other.