The spyglass may be frusto-conical and forced into a similar shaped hole in the wall or door, or be externally screw threaded so as either to be screwed into the hole or inserted from one side and receive an internally threaded locking sleeve screwed on to it from the other side....
had invented a spyglass(小望远镜).He learned that the instrument could show faraway things as if they were nearby.It could magnify(放大)things to appear up to three times bigger!Galileo decided to (6) one of his own.He quickly understood how the spyglass worked and made ...