Rotation of Liquids. 



87 



discrepancies, and that the experimenter is preparing with nice in- 

 struments to determine the forms affected by liquids under various 

 circumstances, and thence to derive a mechanical measure of chemical 

 affinity." We have therefore deemed it expedient to state, that the 

 anomaly of the case is entirely due to the different degrees of adhe- 

 siveness of the liquids which, while the velocity of the apparatus is 

 increasing, causes the most adhesive, to take, almost immediately, 

 the velocity of the jar, while the less adhesive substance is not so 

 soon brought into a rapid rotary motion ; consequently, if the most 

 adhesive liquid is placed at bottom, it will, by taking the velocity of 

 the jar, possess the concave surface, and more so than the upper li- 

 quid, while if the least adhesive substance be below, it will be longer 

 in attaining the velocity ; and, consequently, the centrifugal force of 

 the upper liquid being greatest, it will force itself downwards as well 

 as upwards around the sides of the vessel, forming, so to speak, a 

 " solid of revolution" like a double concave lens. If, however, the 

 rotation be continued long enough to have the liquids both acquire 

 the velocity of the apparatus, the anomaly will disappear so that the 

 lower and less adhesive liquid will present a concave surface as well 

 as the other. In bringing the jar suddenly to rest, the concavity of 

 separation will continue after that of the upper surface has disap- 

 peared. The annexed figure represents a jar 

 placed on a suitable base, and resting on a spin- 

 dle furnished with a pulley for multiplying the 

 speed. The axis being vertical, if we fill the 

 jar to ms with water, and then place upon this 

 a quantity of oil rising to u s, these two lines will 

 represent respectively the surface of separa- 

 tion and the upper surface of the liquids when 

 at rest. As the apparatus begins to revolve, 

 the oil partaking almost immediately of the ve- 

 locity of the jar, while the water obeying its 

 inertia, and possessing less adhesiveness, allows 

 the jar to move with a considerable relative ve- 

 locity, and hence having less centrifugal force 

 than the oil, the latter will not only rise above 

 the line u s, but likewise sink below m s, as in- 

 dicated in the shaded part of the figure. Such, 

 however, will be the appearance no longer 

 than till the apparatus has come to a uniform 



