and sixty degrees—a very clever application of an annular prism with objectives, condenser, and two eyepieces of low and high power."
A call from one of the crew took him into the stern to watch the operation of something, leaving me to myself, for Kennedy was roaming about on a still hunt for anything that might suggest itself. The safety devices, probably more than any other single thing, interested me, for I had read with peculiar fascination of the great disasters to the Lutin, the Pluviöse, the Farfardet, the A8, the Foca, the Kambala, the Japanese No 6, the German U3, and others.
Below us I knew there was a keel that could be dropped, lightening the boat considerably. Also, there was the submarine bell, immersed in a tank of water, with telephone receivers attached by which one could "listen in," for example, before rising, say, from sixty feet to twenty feet, and thus "hear" the hulls of other ships. The bell was struck by means of air pressure, and was the same as that used for submarine signalling on ships. Water, being dense, is an excellent conductor of sound. Even in the submarine itself, I could hear the muffled clang of the gong.
Then there were buoys which could be released and would fly to the surface, carrying within them a telephone, a light, and a whistle. I knew also something of the explosion dangers on a submarine, both from the fuel oil used when running on the surface, and from the storage batteries used when running submerged. Once in a while a sailor would take from a jar a piece of litmus paper and expose it, showing only a slight discolouration due to carbon dioxide.
