There are more particulars given of Charles Darnay's appearance than there are of Sydney Carton's in A Tale of Two Cities. As it is generally agreed that the two men are remarkably alike, however, the reader may infer that the general comments about Darnay's appearance apply also to Carton.
Sydney Carton, therefore, is a young man in his twenties. He has dark hair, dark eyes, and a healthy, well-proportioned physique. So far, Darnay and Carton are the same; however, whereas Darnay is neatly dressed and quietly confident in his manner, Carton is slovenly and has a defeated, cynical air about him.
It is easy for the reader to forget how closely Carton resembles Darnay. The resemblance is close enough to sow doubt in the minds of the jury at Darnay's trial, but Carton is continually described in degrading terms as a failure and a drunkard. In particular, Dickens characterizes the relationship between the pompous, talentless Stryver and Carton as that of a lion to a jackal. While he does not say that Carton looks like a jackal, such comparisons have the effect of leading the reader to imagine Carton as a mangy, miserable figure, despite the lack of explicit physical description to this effect.