Sentence:  ...to suppose that the general concern of this Country can be directed by thirteen heads, or one head without competent powers, is a <WSD>solecism</WSD>, the bad effects of which every Man who has had the practical knowledge to judge from, that I have, is fully convinced of; tho' none perhaps has felt them in so forcible, and distressing a degree. 
Meaning of the word marked with <WSD> tags:  An erroneous or improper usage.