Sentence:  The Begums' ministers, on the contrary, to extort from them the disclosure of the place which concealed the treasures, were, ... after being "fettered" and "imprisoned", led out on to a <WSD>scaffold</WSD>, and this array of terrours proving unavailing, the "meek" tempered Middleton, as a dernier resort, menaced them with a confinement in the fortress of Chunargar. Thus, my lords, was a British garrison made the "climax" of "cruelties"! 
Meaning of the word marked with <WSD> tags:  An elevated platform on which a criminal is executed.