a pair of compasses meaning in Chinese

一个圆规
一只圆规

It is easy to describe a circle if you have a pair of compasses
如果你有一副圆规,就很容易画一个圆。
They had never been worn , my mother said . under that , the miscellany began - a quadrant , a tin canikin , several sticks of tobacco , two brace of very handsome pistols , a piece of bar silver , an old spanish watch and some other trinkets of little value and mostly of foreign make , a pair of compasses mounted with brass , and five or six curious west indian shells
在那套衣服的下面，开始出现了各式各样的东西：一个四分仪，一个锡制的小酒杯，几颗烟，两对非常漂亮的手铣，一根银条，一只西班牙老怀表，还有其他一些不值钱的小装饰品，大多是外国制造的，一副黄铜杆的圆规，还有五六个珍奇的西印度贝壳。