The other mechanism in the interior of the boat is simple and self-explanatory. There were two anchors with windlasses, one anchor to hold in the usual manner against drifting, the other to regulate depth when lying stationary. There were pumps for emptying the water ballast chambers. On deck was a conning tower quite similar to the tower on a modern submarine, which served when closed as a lookout for the helmsman, and when open as means of ingress and egress for the crew. This conning tower had glass windows through which an observer could watch big prey, or steer his course when the boat was partially submerged. Plate Fifth shows how the conning tower could be used when it should be the only part of the vessel above the surface. This particular plate is of peculiar interest in that Fulton has drawn a picture of himself looking through the glass-covered ports. In the original drawing the head is full size. Attached to the conning tower were two pipes marked _F_ and _G_ in Plate Second. These pipes led to the interior of the boat and permitted fresh air to be drawn in, and the vitiated or mephitic air (as Fulton called it) expelled. These pipes permitted the boat to be submerged so that the deck was just awash, the only part above the surface being the upper half of the conning tower and the air pipes. This is the situation as shown in Plate Fifth. So operated, the boat did not differ materially from a modern submarine under similar conditions with her periscope out of water. From Fulton’s small conning tower he had only direct vision. A periscope enables the boat to be wholly submerged with vision obtained by reflecting mirrors. But a boat submerged so as to be just awash, with only the conning tower showing, and driven by a hand-operated propeller could have entered at night unseen almost any harbor, because in those days there were no powerful searchlights to illuminate the surface of the water at a distance. The British were right in the secret note that they sent to the naval commanders that Fulton’s boat, even without the later improvements that he showed the British Government, could in the hands of the French have made an attack with very serious results upon an open roadstead such as the mouth of the Thames. According to modern phraseology, Fulton’s British boat was a submersible rather than a submarine. The latter term defines a vessel that has powers of offense under water by torpedoes that in turn have means of locomotion. With such a torpedo neither Fulton nor the art was acquainted. His torpedoes or “bombs” were immobile affairs intended to be anchored, dragged by a boat or allowed to drift with the tide and to explode by concussion.