To prevent leakage of gas from within {TAIL ~ the cell} {HEAD ~ the substrates} have sealing areas 24 at opposite edges to cooperate with the sealing surfaces on the plates 
To prevent leakage of gas from within { TAIL ~ the cell } { HEAD ~ the substrates } have sealing areas 24 at opposite edges to cooperate with the sealing surfaces on the plates
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH