By providing two movable members the dip rings carried thereby may be of different sizes and arranged oppositely in {HEAD ~ their first and second positions} to emit {TAIL ~ an essentially continuous stream} of alternately large and small bubbles 
to emit
By providing two movable members the dip rings carried thereby may be of different sizes and arranged oppositely in { HEAD ~ their first and second positions } to emit { TAIL ~ an essentially continuous stream } of alternately large and small bubbles
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH