72 
On the Action of Rain to calm the Sea,” by Professor 
Osborne Reynolds, M.A. 
There appears to be a very general belief amongst sailors 
that rain tends to calm the sea, or as I have often heard it 
expressed, that rain soon knocks down the sea. 
Without attaching very much weight to this general 
impression, my object in this paper is to point out an effect 
of rain on falling into water which I believe has not been 
hitherto noticed, and which would certainly tend to destroy 
any wave motion there might be in the water. 
When a drop of rain falls on to water the splash or 
rebound is visible enough, as are also the waves which 
diverge from the point of contact ; but the effect caused by 
the drop under the surface is not apparent, because the 
water being all of the same colour there is nothing to show 
the interchange of place which may be going on. There is 
however a very considerable effect produced. If instead of 
a drop of rain we let fall a drop of coloured water, or better 
still if we colour the topmost layer of the water, this effect 
becomes apparent. We then see that each drop sends down 
one or more masses of coloured water in the form of vortex 
rings. These rings descend with a gradually diminishing 
velocity and with increasing size to a distance of several 
inches, generally as much as 18, below the surface. 
Each drop sends in general more than one ring, but the 
first ring is much more definite and descends much quicker 
than those which follow it. If the surface of the water be 
not coloured this first ring is hardly apparent, for it appears 
to contain very little of the water of the drop which causes 
it. The actual size of these rings depends on the size and 
speed of the drops. They steadily increase as they descend, 
and before they stop they have generally attained a 
diameter of from 1 to 2 inches, or even more. The annexed 
cut shows the effect which may be produced in a glass 
vessel. 
