The success of ball pen was based upon a viscous, oil-based ink. Early ballpoint pens did not write well; they tended to skip, and the slow-drying oil-based ink smudged easily.
- ball pen [bɔ:l - pen] n. 圆珠笔
- viscous [ˈviskəs] adj.黏性的
- skip [skip] v. 滑，笔触中途不出油
- smudge [smʌdʒ] v. 弄脏，涂去，使模糊
