fourth cylinder 30 notably the inner cavity 38 remains substantially uncompressed it is important that compression of the inner cavity 38 be limited in order to not excessively impede flow of the acetylene gas through the fifth cylinder one method of compressing the upper portion of the fifth cylinder while limiting compression of the inner cavity illustrated in fig3 c is to insert a solid wire into the upper portion of the inner cavity prior to compression with the solid wire inserted a compressive force is applied to the upper end of the fifth cylinder as illustrated by the arrows in fig3 c this may be done by placing the fifth cylinder on a solid surface and striking the upper end with a hammer the compressive force partially flattens the upper end while the inserted solid wire limits compression of the inner cavity the solid wire is then removed the solid wire is selected have a diameter slightly less than the inner diameter of the fifth cylinder to permit ready insertion and removal of the wire the precise diameter of the solid wire may be selected to permit a desired amount of compression of the inner cavity although the desired amount of compression.