Apparatus 36 includes a tube 37, having {HEAD ~ a pump} 38 at {TAIL ~ one end} and gas entry pipes 39 and 40 shown for convenience as being at the other end 
at
Apparatus 36 includes a tube 37 , having { HEAD ~ a pump } 38 at { TAIL ~ one end } and gas entry pipes 39 and 40 shown for convenience as being at the other end
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH