A short mast, called a _stanchion_, is also fixed to the conning tower and this carries the signal lights and holds one end of the aerial, the other end being fastened to the stern. It isn’t much of an aerial but as our submarine was built for coast patrol cruising we were never very far from shore. The inside of the hull is partitioned off into rooms, or compartments, and these can be shut off from each other by means of bulkhead doors and so made watertight. The purpose of these watertight compartments is to prevent the water from filling the whole boat if she should be unlucky enough to be hit by a shell or rammed by a ship. To my way of thinking watertight compartments seem to be of little use whether the boat be a submarine or the largest ship. For instance when the _Titanic_ was scrapped by an iceberg and the _Lusitania_ was hit by a U-boat torpedo they both went down in a few minutes. I won’t try to tell you what all the different compartments have in them but some of them are most uncommonly interesting and these you should know about. The first is the conning tower with its _periscope_. When the submarine is running either light or awash and the weather is good the commander can see what’s what around him from the deck or from the _bridge_, as we call the top of the conning tower. When the weather is rough or an enemy is nigh he takes a look around through the ports, that is, watertight windows, in the conning tower. Should, however, the boat be submerged and the captain wants to size up the situation he permits only the top of her periscope to project out of the water and through this he scans the sea. Whenever I got a chance I used to look through the periscope. At first it was hard for me to make out a vessel on the surface because the field of view was small and what with the boat rolling from port to starboard it seemed to me I was always looking at the water or the sky; but after awhile I got so I could take in whatever there was to see in between times. Our submarine had two periscopes, one of the older kind that you have to turn around in order to see the whole horizon, and the other, which was the latest style, showed the whole horizon at once with a magnified view of the ship or other vessel in the distance in the center. This scheme was a great invention as it prevented us from being attacked from behind unawares. It was like having a third eye in the back of your head. Inside the conning tower are also speaking tubes and an electric system of lights and bells worked by pushbuttons and these run into all the compartments; by means of these intelligence transmission systems our captain could get in touch instantly with the chiefs of the crew in the engine, diving, torpedo and wireless rooms.