Portholes

Some articles on portholes, porthole:

Malting House School - Operation
... Dan corrected her, emphatically, "They're not windows, they're portholes" ... said, "Yes, they're portholes, but then portholes are windows" ...
Submarine Portholes
... Portholes on submarines are generally made of acrylic plastic ... In the case of deep diving submarines, the portholes can be several inches thick ...
Porthole - Structure
... A porthole consists of at least two structural components and is, in its simplest form, similar to any other type of window in design and purpose ... The porthole is primarily a circular glass disk encased in a metal frame that is bolted securely into the side of a ship's hull ... Sometimes the glass disk of a porthole is encased in a separate frame which is hinged onto the base frame so that it can be opened and closed ...