Apparently, you remove the chimney, to light the wick.
http://www.weems-plath.com/pdf/customer-service.pdf
.}{1 Instructions for use of the
oil burners
Follow these tips to ensure that you get many years of use from your oil burner.
.}{1 Remove the oil holder from the lamp before filling it with lamp oil.
.}{2 Remove the lamp chimney and carefully unscrew the burner (be careful not to use the stem of the burner as a lever when doing this).
.}{3 Fill the oil holder approximately 3/4 full with pure petroleum or a colorless lamp oil.
.}{4 Screw the burner back on the oil holder again. Leave the wick to become fully saturated for approximately 30 minutes.
.}{5 Turn up the wick until it emerges just above the wick holder.
.}{6 If necessary, trim the wick level using a pair of scissors or sharp knife.
.}{7 After
lighting the wick, replace the lamp chimney and keep the flame low until the cold glass has time to warm so as to prevent the glass from cracking.
.}{8 Now adjust the flame such that there is no smoke. When the lamp is first used this adjustment will need to be repeated a number of times as the wick stretches.
.}{9 To extinguish the burner, turn the wick down until the flame goes out.
.}{10 Allow the lamp chimney to cool before relighting the lamp.
.}{11 To prevent the swollen wick from damaging the turning mechanism of burners, it is recommended that the wick be replaced on an annual basis.