谁帮我翻译下这段英语

In the middle of the city place a marble amussium,laying it true by the level,or else let the spot be made so true by means of rule and level that no amussium is necessary.In the very centre of that spot set up a bronze gnomon or "shadow tracker".At about the fifth hour in the morning,take the end of the shadow cast by this gonmon,and mark it with a point.Then,opening your compass to this point which marks the length of the gonmon's shadow,describe a cricle from the centre.In the afternoon watch the shadow of your gonmon as it lengthens,and when it once more touches the circumference of this circle and the shadow in the afternoon is equal in lenth to that of the morning,mark it with a point.

在这城市的中央放置着一个大理石日月贝，它真实明显地放在这个水平高度，要不然用常用的方法水平用斑点来使它真实来让这日月贝显的不那么重要。在这个斑点的正中在装一个青铜指南针或“追影仪”。在早上5点的时候，用这青铜器截取最后的投影，以一个点做标记。然后，打开你的指南针朝着这个标记着长度的投影，在中央描绘一个cricle（是不是圆circle啦？）在下午来观察这个延伸的投影，当它再次碰到这个圆的圆周并且和的那个长度一样，在以个点做标记。