Question about Ocean going Ships/boats?

Question

Ok, so what is that round thing on the window? Watching shows like "Deadliest Catch" on Discovery and PBS' "Carrier", I've noticed these round things on on pane of the front window of the bridge or windshield or whatever you call it on a boat. It is a round thing with a wire leading away. What is it, what does it do?

Thanks, i know nothing about boats or nautical stuff.

Answer 1

a compass

Answer 2

and the trade name for the spinning disk is "The Kent Clear View"

Answer 3

It's a disk of glass that spins. This is used in place of a windshield wiper. The spinning disk spins the water away so you can see through it.

Answer 4

Thats a window that spins in bad weather. Water gets spun off the glass so you don't need windshield wipers.