a stationary cylindrical casing comprising {TAIL ~ a pair} of opposite gables, enclosing said rotatable drum, whereby an annular space is defined between {HEAD ~ said stationary cylindrical casing} and said rotatable drum, 
a stationary cylindrical casing comprising { TAIL ~ a pair } of opposite gables , enclosing said rotatable drum , whereby an annular space is defined between { HEAD ~ said stationary cylindrical casing } and said rotatable drum ,
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH