A HISTORY OF SCIENCE 



horizontal base, the oblique sides bearing the relation 

 to each other of two to one. Stevinus found that his 

 chain of balls just balanced when four balls were on 

 the longer side and two on the shorter and steeper 

 side. The balancing of force thus brought about con- 

 stituted a stable equilibrium, Stevinus being the first 

 to discriminate between such a condition and the un- 

 balanced condition called unstable equilibrium. By 

 this simple experiment was laid the foundation of the 

 science of statics. Stevinus had a full grasp of the 

 principle which his experiment involved, and he ap- 

 plied it to the solution of oblique forces in all direc- 

 tions. Earlier investigations of Stevinus were pub- 

 lished in 1608. His collected works were published at 

 Ley den in 1634. 



This study of the equilibrium of pressure of bodies 

 at rest led Stevinus, not unnaturally, to consider the 

 allied subject of the pressure of liquids. He is to be 

 credited with the explanation of the so - called hy- 

 drostatic paradox. The familiar modern experiment 

 which illustrates this paradox is made by inserting a 

 long perpendicular tube of small caliber into the top of 

 a tight barrel. On filling the barrel and tube with 

 water, it is possible to produce a pressure which will 

 burst the barrel, though it be a strong one, and though 

 the actual weight of water in the tube is comparatively 

 insignificant. This illustrates the fact that the press- 

 ure at the bottom of a column of liquid is propor- 

 tionate to the height of the column, and not to its 

 bulk, this being the hydrostatic paradox in question. 

 The explanation is that an enclosed fluid under press- 

 ure exerts an equal force upon all parts of the cir- 



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