160 THE QUAQUAVERSUS PRESSURE OF FLUIDS. 



empty bottle, a cork of such a large size, that one half of it remained 

 above the neck : a cord was then tied round the cork and fastened to 

 the neck of the bottle, and a coating of pitch was put over the whole. 



When the bottle was let down to the depth of about fifty fathoms, 

 he perceived by the additional weight, that it had instantly filled ; 

 and on drawing it up, the cork was found in the inside of the bottle, 

 which of course was filled with water. 



Another bottle was prepared in a similar manner ; but in order to 

 secure the cork, and to prevent it from being pressed within the bottle, 

 a sail needle was passed through it, so as just to rest on the margin of 

 the glass, and the whole was carefully covered with a coating of pitch. 



When the bottle had descended to the depth of about fifty fathoms, 

 as in the former case, it was again perceived to have been filled with 

 water; and on bringing it to the surface, the cork and needle were 

 found in the same position, and no part of the pitch appeared to be 

 broken, although the bottle was completely filled with water. Here 

 the water must have insinuated itself through the pores of the pitch 

 and the cork, and not as the experimentalist supposes, through the 

 pores of the glass. 



The equality of fluid pressure in every direction, is very easily 

 demonstrated in the following manner. 



EXPERIMENT 7. If a piece of very soft wax, as GUI, and the egg 

 E, be placed in a bladder, or some other flexible vessel filled with 

 water, and if the bladder be put into a brass box, and a moveable 

 cover laid upon the bladder so as to be wholly supported by it. 



Then, if one hundred, or one hun- 

 dred and fifty Ibs. be laid upon this 

 cover, so as to press upon the bladder 

 and its contained fluid ; this enor- 

 mous force, although propagated 

 throughout the fluid, and acting 

 upon the soft wax and the egg, will 

 produce no effect, the wax will not 

 change its form, and the egg will not be broken. And in like manner, 

 if a living fish should be put into the cylinder of a hydrostatic press, when 

 under a very high degree of pressure, it will not suffer the least incon- 

 venience ; from which it is obvious that every particle of the fluid is 

 equally pressed, and presses equally in all directions. 



Numerous other examples might be adduced for proving the same 

 thing, but since the principle is manifest, it is needless to dwell longer 

 on the subject. 



