Thus, {TAIL ~ the number} of {HEAD ~ times} gas escapes from the valve can be counted 
Thus , { TAIL ~ the number } of { HEAD ~ times } gas escapes from the valve can be counted
OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH