Common Science 



FIG. 23. The mercury does not wet the finger, and as th 

 mercury does not follow it. 



lifted the 



in Experiment 14. When you pull your finger all the way 

 out, has the mercury wet it at all? Put a lamp wick or a 

 part of your handkerchief into the mercury. Does it draw 

 the mercury up as it would draw up water? 



The reason for this peculiarity of mercury is that the 

 pull between the particles of mercury themselves is 

 stronger than the pull between them and your finger 

 or handkerchief. In scientific language, the cohesion 

 of the mercury is stronger than its adhesion to your 

 finger or handkerchief. Although this seems unusual 

 for a liquid, it is what we naturally expect of solid things ; 

 you would be amazed if part of the wood of your school 

 seat stuck to you when you got up, for you expect the 

 particles in solid things to cohere to have cohesion 

 much more strongly than they adhere to something else. 

 It is because solids have such strong cohesion that they 

 are solids. 



