Sentence:  That it will, however, cause the subscribers to wish, in their minds, for many oaths to fly about, which is a heinous crime, and to lay stratagems to try the patience of men of all sorts; to put them upon the swearing strain, in order to bring <WSD>grist</WSD> to their own mill, which is a crime still more enormous; and that therefore, for fear of these evil consequences, the passing of such an act is not consistent with the really extraordinary and tender conscience of a true modern politician. 
Meaning of the word marked with <WSD> tags:  Grain that is to be ground in a mill.