OBJECTS.] INTRODUCTORY. 37 



12,625 grains, half; if 16,832 grains, it would sink two- 

 thirds of its volume, and so on. Or, if, when the box 

 is floating, you make a mark upon its side at the exact 

 level of the surface of the water, the bulk of that 

 portion of the box which lies below the water-level 

 can be ascertained. Suppose it to be thirty cubic 

 inches, then the weight cf the box will be 30 x 252-5 

 or 7575 grains. Hence it may be said that the im- 

 mersed part of a floating body takes the place of the 

 water which it displaces, and, as it were, represents 

 it. If you press downwards upon the floating box, 

 there is a feeling of resistance as it descends, and 

 when the pressure is taken off, the body immediately 

 rises again. Hence the water presses upwards against 

 the bottom of the floating body. But it also presses 

 against the sides, for if the sides of the box are very 

 thin they will be driven in. If a thin empty bottle is 

 tightly corked and lowered into deep water the cork 

 will be driven in, or else the bottle will be crushed. 



27. Water Presses in all Directions. 



Thus water presses in all directions upon things 

 which are immersed in it. 



If a long wooden or metal pipe, placed vertically, 

 has its lower end stopped with a cork which does not 

 fit very tightly, and water is poured into the top of the 

 tube, the water will at first fill the part of the tube 

 above the cork, and its weight will exert a certain 

 pressure on the cork. In fact, if the end of the 

 tube is stopped by applying the palm of the hand 

 closley against it, the downward pressure of the 

 water will have to be overcome by a certain amount 

 of effort As the water accumulates, this downward 



