As the bell descends below the surface, the pressure of the air becomes very great, being equal to the pressure of the water. A dense atmosphere of this sort has many peculiarities. It is easy enough to breathe, but the pressure on the drum of the ear is frequently inconvenient. An ordinary whisper will sound as loud as the customary tones of the voice, and if there are two persons in the bell, and one of them speaks as he would naturally speak in the open air, he will seem to the other to be shouting with the full power of his lungs. A slight blow upon any metallic substance within the bell will sound like a very heavy one, and any noise that would cause no inconvenience in the open air may become absolutely painful in the dense atmosphere in the inside of a diving-bell. A diving-bell must be made very heavy to carry it downward, and large weights are generally placed around its mouth. A shelf inside serves as a seat for the occupant, and when it is lowered to the bottom, the ground can be leisurely surveyed or examined for whatever object the diver has in view. Sometimes, when two persons descend in a bell, one of them may leave the bell by diving into the water, and then returning, but he cannot go very far. Submarine armor, however, enables him to go quite a distance away from the bell, and return at his leisure. Submarine armor possesses many advantages over the ordinary diving-bell. A man encased in a submarine suit can remain under water for a long time, and move about pretty much as he likes. [Sidenote: SUBMARINE ARMOR.] Submarine armor consists of a water-proof suit, completely encasing the body of the wearer. It is put on in two sections; the trousers have shoes attached to them, with heavy leaden soles, and at the waist they are firmly fastened to a metallic ring. The upper part of the suit covers the arms, the head, and the chest, and the lower part of it is fastened to a ring which exactly meets the other. The upper part of the suit is put on, and after it the second, or lower part. The two rings are then fastened together by means of screws, and a thin band of rubber upon them excludes both air and water. The head of the diver is enclosed in a helmet made of brass or other metal, and having a thick plate of glass in front. Air is conveyed inside this helmet by means of a rubber tube, and an air pump must be kept in constant operation, to supply the man in armor with the necessary amount of air. The foul air escapes through a valve in the top, just as it escapes from the top of the diving-bell. A suit of clothing of this sort does not add to the beauty of its wearer; it is very cumbersome, and I greatly doubt if it ever becomes fashionable for an afternoon promenade on Broadway. The helmet might answer very well as a disguise, for the reason that the face of the wearer is almost, and generally quite, invisible.