Sentence:  But then I had the [massive] flintlock by me for protection. ¶...The linen-press and a chest on the top of it formed, however, a very good gun-carriage; and, thus mounted, aim could be taken out of the window [...], and a 'bead' could be drawn upon Molly, the dairymaid, kissing the fogger behind the hedge, little dreaming that the deadly <WSD>tube</WSD> was levelled at them. 
Meaning of the word marked with <WSD> tags:  Anything that is hollow and cylindrical in shape.