1.   A drifting cloud disappeared against some invisible line and began to emerge in another part of the sky altogether.

2.   Bobbie exhorted, as we sat staring at the invisible line that stretched beyond us.

3.   She felt as though an invisible line through her backbone held her upright.

4.   Invisible lines form the network of our existence.

5.   The invisible lines, which traced the patterns of their existence, merged into one.

6.   The problem can more easily arise for young academics, who are close in age to their students and do not know when they are crossing an invisible line.

7.   An invisible line kept African-Americans and Hispanics from living in the center of the city.

8.   An invisible psychic line has long separated laborers, many of whom live in Napa, from the Valley.

9.   But his conduct provoked Democrats to complain that an important invisible line had been crossed between legitimate partisan debate and intolerable disrespect.