COHESIVE FORCE OPPOSED TO GRAVITATION. #3 



fluid is of the same specific gravity as olive oil. If, when 

 this is effected, we drop globules of the oil into the 

 mixed fluid, it will he seen that they take an orbicular 

 form ; and, of course, in this experiment the power of 

 the earth's gravitating influence is neutralized. The 

 same drops of oil under any other conditions would be 

 flattened. Simple as this illustration is, it tells much of 

 the wondrous secret of those beautifully balanced forces 

 of cohesion and of gravitation; and from the prosaic 

 fact we rise to a great philosophical truth. Our experi- 

 ment may lead us yet farther in exemplification of 

 known phenomena. If we pass a steel wire through 

 one of those floating spheres of oil, and make it revolvo 

 rapidly and steadily, thus imitating the motion of . 

 planet on its axis, the oil spreads out, and we have thk 

 spheroidal form of our earth. Increase the rapidity of 

 this rotation, and when a certain rate is obtained the 

 oil widens into a disc, a ring separates itself from 

 a central globe, and at a distance from it still revolves 

 around it.* Here we have a miniature representation of 



* The experiment alluded to is one of a series by M. Plateau, 

 who thus describes his arrangement of the fluid : " We begin by 

 making a mixture of alcohol and distilled water, containing a cer- 

 tain excess of alcohol, so that when submitted to the trial of the 

 test tube it lets the small sphere of oil fall to the bottom rather 

 rapidly. When this point is obtained, the whole is thrown upon 

 filters, care being taken to cover the funnels containing these last 

 with plates of glass; this precaution is taken in order to prevent, 

 as much as possible, the evaporation of the alcohol. The alco- 

 holic liquor passes the first through the filters, ordinarily carrying 

 with it a certain number of very minute spherules of oil When 

 the greater part has thus passed, the spherules become more nume- 

 rous; what still remains in the first filters, namely, the oil and a 

 residue of alcoholic liquor, is then thrown into a single filter placed 

 on a new flask. This last filtration takes place much more slowly 

 than the first, on account of the viscosity of the oil ; it is consider- 

 ably accelerated by renewing the filter once or twice during the 

 operation. If the funnel has been covered with sufficient care, the 

 oil will collect into a single mass at the bottom of the flask uncle 



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