64 DIVING BELL 



swinging pulleys, placed in the piano of the centre of gravity of the nautilus, and 

 thence to the points of affixment respectively (fig. 631). The object to be gaim-d by 

 having the swinging pulleys in the plane of the centre of gravity of the mass, is to 

 hold the machine steady and to prevent oscillation. Within the machine, and directly 

 over the above stuffing boxes, are windlasses for winding in the cables. By working 

 these windlasses movement may bo effected, and of course the number of these cables 

 will depend on the variable character of the situation to be occupied. Having thus 

 secured the means of descending, communicating with the bottom, and of movement, 

 the next point is to ascend. Weight of water has caused a destruction of buoyancy 

 at first, and consequent sinking; if then any portion of this water is removal. an 

 upward effort will at once be exerted exactly proportionate to the weight of water 

 thrown off. The air in the receiver at the surface being constantly maintained at a 

 higher density than that of the water below, if we open the water cock on the top 

 pipe, c c, throwing the condensed air from the receiver above directly on to the 

 surface of the water in the chambers, movement and consequent expulsion of tho 

 water must take place, and an upward movement of the machine itself, which will 

 rise to the surface. 



It is evident that if, previously to the expulsion of the water, the nautilus be affixed 

 to any object below, the power exerted on that object will be exactly proportionate to 

 tho weight of water expelled, and the power will continue increasing until, there 

 being no farther weight to be thrown off, the maximum effect is produced. To apply 

 this power to lifting masses of stone or rock, proper arrangements are affixed to the 

 centre of the opening in the bottom, by which connection can be made with the 

 weight, admitting, at the same time, the swinging around of tho object suspended, 

 so that it may be placed in any required position. In the construction of permanent 

 work, or the movement of objects whose weight is known, or can be estimated, a 

 water, or, so called, lifting tube is placed on the side of the water chamber, which in- 

 dicates the lifting power exercised by the nautilus at any moment. The advantage 

 of this gauge will be recognised, inasmuch as without it the closest attention of the 

 operator, working very cautiously, would be necessary to determine when the weight 

 was overcome : by its aid, however, the operator boldly throws open all the valves 

 necessary to develop the power of the nautilus, watching only the gauge. The water, 

 having reached the proper level indicating the required lifting power, he knows tho 

 weight must be overcome, or so nearly so that the valve or cocks may be at once 

 closed, in order that the movement may take place horizontally. A moment's re- 

 flection will show that, if there were not an index of this character, carelessness or 

 inattention on the part of the operator, by leaving the cocks open too long, might 

 develope a power greater than required, and the nautilus would start suddenly up- 

 ward. The expansive power of air, acting upon the incompressible fluid, water, 

 through the opening in the bottom, gives a momentum which, by successive develop- 

 ments of expansion in the working chamber, is constantly increasing in velocity, 

 until, in any considerable depth of water, the result would be undoubtedly of a very 

 serious character. Take, for exemplification, the nautilus in thirty-three feet of 

 water, and bottom covers removed, and an equilibrium, at fifteen pounds to the inch, 

 existing between the air and the water at the level of tho bottom of tho machine. 

 Upward movement is communicated the instant the machine rises in the slightest 

 degree, the existing equilibrium is destroyed, and tho highly elastic qualities of air 

 assume preponderance, exerting, from the rigid surface of tho water below, an im- 

 pulsive effort upward in the direction of least resistance. At each successive moment 

 of upward movement the impelling power increases, owing to the increasing disparity 

 between the pressure of air within struggling for escape. The machine, thus ntOBted, 

 becomes a marine rocket (in reality), in which the propelling power is exhausted only 

 when the surface is reached, and a new equilibrium is obtained. It will readily bo 

 seen that, were this difficulty not overcome, it would be impossible to govern tho 

 nautilus ; for, rising with great velocity to the surface, the machine is carried above 

 its ordinary flotation, or water lino, a little more air escaping owing to tho diminished 

 resistance as that level is passed ; the recoil, or surging downwards, causes a conden- 

 sation of the air remaining in the chamber ; a portion of tho space previously oivujiiri I 

 by air is assumed by water ; tho buoyant power becomes less, tho machine settles 

 slightly more by condensation of the air, a larger spice is occupied by water, and the 

 nautilus redescends to the bottom with a constantly accelerating movement, seriously 

 inconveniencing the operator by filling more or less with water, according to ! jitli. 

 For many months the difficulties just enumerated baffled all ;ittempts at control. A 

 weight attached could be lifted, but tho instant it was entirely suspended, before the 

 valves could be closed, upward movement was comnmnieaii <1 beyond control. This 

 difficulty so fatal has been overcome by an arrangement at the bottom of the nautilus, 

 with channels which radiate from tho opening in an inclined direction, debouching at 



