Assertion: clarinet's instrument | /r/HasAspect | three vanes
Facets:
value: to observe the horizon
type: PURPOSE
Source sentences:
text: The instrument has three vanes, a horizon vane (A in Figure 8) which has an opening in it to observe the horizon, a shadow vane (B) to cast a shadow on the horizon vane and a sighting vane (C) that the navigator uses to view the horizon and shadow at the horizon vane.