468 Scientific Intelligence. 
like mercury and water, or oil of turpentine and water, ripples 
are not made; but if powdered quartz or barite covers the 
cury a mixture of some viscosity is produced by the friction and 
ripples will form. 
Ripples are then the result of oscillatory or intermittent fric- 
tion. A wave, whether stationary or propagating itself, sepia 
)a 
. 
impact and oscillatory friction; and this 
pronounced when the motion of the liquid consists in a simpl 
uninodal undulation. No general movement of the mass 1s 
against which the wave acts experiences simultaneously a normal 
fri 
ary. 
Thus, the problem of the formation of rippled surfaces is that 
I i stat 
ee 
ment of the author’s general conclusion is followed by an account 
of his various experiments, in illustration of which there are four 
between the ripples was always the same if the amplitude 0 
oscillation and depth were the same. Other experiments were 
and their 
before, on the amplitude of the oscillatory friction. 
form, the author quotes an article by the brothers E. 
