1. Willow在科学期刊上看到用手表当指南针的试验，对此非常感兴趣。请根据图片内容，补全Willow所述内容，邀请好友共同试验。每空仅填一词。

I got the idea about how to use a to find the north. Do you want to have a try? Before starting, we have to choose a day. Prepare a watch, a compass and two small . Here are the steps. First, lay the watch flat and point the hour hand toward the sun. Second, find the direction halfway between the hour hand and 12. The direction points south. And the other side of the watch shows the . Finally, use the compass to check the . The watch and compass will point in almost exactly the same direction.