THE EARTH. 161 



filled with water be forty feet high, the bottom of 

 that vessel will sustain such a pressure as would 

 raise the same water forty feet high, which is very 

 great. From hence we see how extremely apt 

 our pipes that convey water to the city are to 

 burst ; for, descending from a hill of more than 

 forty feet high, they are pressed by the water 

 contained in them, with a force equal to what 

 would raise it to more than forty feet high ; and 

 that this is sometimes able to burst a wooden 

 pipe, we can have no room to doubt of* 



Still recurring to our pipe, let us suppose one 

 of its arms ten times as thick as the other : this 

 will produce no effect whatsoever upon the ob- 

 stacle below which we supposed to hinder its rise 

 in the other arm ; because, how thick soever the 

 pipe may be, its contents would only rise to its 

 own level ; and it will, therefore, press the ob- 

 stacle with a force equal thereto. We may, there- 

 fore, universally conclude, that the bottom of a 

 vessel is pressed by its water, not as it is broad or 

 narrow, but in proportion as it is high. Thus the 

 water contained in a vessel not thicker than my 

 finger, presses its bottom as forcibly as the water 

 contained in a hogshead of an equal height j and 

 if we made holes in the bottoms of both, the water 

 would burst out as forceful from the one as the 

 other. Hence we may, with great ease, burst a 

 hogshead with a single quart of water ; and it has 

 been often done. We have only,* for this, to 

 place a hogshead on one end, filled with water $ 



* Nollet's Lectures. 

 VOL. I. L 



