I.on [美 ɑn, ɔn, 英 ɒn]介词on often appears as the second element of certain verb structures in English (count on, lay on, sign on, etc). For translations, see the relevant verb entry (count, lay, sign, etc).
The craziness with which he has handled this matter radiates from each drawing: heavy black lines and contours of a figure on a chair in an empty room.