said plate member and said floor further cooperating to allow gas to seep from said compartment to said chamber for providing {TAIL ~ a substantially uniform gaseous environment} in said {HEAD ~ chamber} 
said plate member and said floor further cooperating to allow gas to seep from said compartment to said chamber for providing { TAIL ~ a substantially uniform gaseous environment } in said { HEAD ~ chamber }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD