.Ebullition of Rotating Water. 



333 



column and at any moment occupying a horizontal plane, tra- 

 verses the water from top to bottom, and spreads out in so doing, 

 apparently causing in its course the partial or almost complete 

 condensation of the steam and the curious brief downward 

 movement of the bubbles left : at the same time the surface 

 of the water in the beaker becomes deeply indented, perhaps 

 sinking in to take the place of the steam which has condensed, 

 (though the writer does not feel at all certain that this is the 

 •cause of the depression formed). This second part of the 

 pulsation is illustrated by fig. 3. After this the apex of the 



Fio-. 3. 



Fijr. 4. 



surface vortex rises, and the first phase of the phenomenon 

 recurs. This state of pulsations continues for perhaps three 

 or four minutes: the eruptions of steam are very violent 

 towards the close of the period, especially if the water has 

 been boiled for long, or is made slightly alkaline (the con- 



CO J_ 



ditions for boiling with bumping), and fig. 4 shows the etrect 

 of such a condition of things. The original photograph was 

 taken midway through the pulsation period and in the 2nd 

 phase. In this photograph it will be noticed that the point 

 where the steam was first formed is not on the surface of the 

 beaker as it generally is, but in the water itself. Some other 

 photographs were taken at the close of the pulsation period, 

 when the axis of rotation of the water begins to " wobble," 

 and consequently the point where the steam is formed is not, 

 as a rule, in the geometrical vertical axis of the beaker. Soon 

 after this " wobbling " sets in the steam begins to be formed 

 anywhere, at, or near, the bottom of the beaker — and all 

 evidence of the effects of rotation vanishes. 



The curve of the surface of the water throughout is never 

 a parabola, as it would be if the angular velocity of the water 

 were everywhere equal : thus the divergence from the para- 

 bolic form indicates how very much more rapidly the water 



