Eye by Light, are they not of a
vibrating nature?

_Qu._ 17. If a stone be thrown into stagnating Water, the Waves excited
thereby continue some time to arise in the place where the Stone fell
into the Water, and are propagated from thence in concentrick Circles
upon the Surface of the Water to great distances. And the Vibrations or
Tremors excited in the Air by percussion, continue a little time to move
from the place of percussion in concentrick Spheres to great distances.
And in like manner, when a Ray of Light falls upon the Surface of any
pellucid Body, and is there refracted or reflected, may not Waves of
Vibrations, or Tremors, be thereby excited in the refracting or
reflecting Medium at the point of Incidence, and continue to arise
there, and to be propagated from thence as long as they continue to
arise and be propagated, when they are excited in the bottom of the Eye
by the Pressure or Motion of the Finger, or by the Light which comes
from the Coal of Fire in the Experiments above-mention'd? and are not
these Vibrations propagated from the point of Incidence to great
distances? And do they not overtake the Rays of Light, and by overtaking
them successively, do they not put them into the Fits of easy Reflexion
and easy Transmission described above? For if the Rays endeavour to
recede from the densest part of the Vibration, they may be alternately
accelerated and retarded by the Vibrations overtaking them.

_Qu._ 18. If in two large tall cylindrical Vessels of Glass inverted,
two little Thermometers be suspended so as not to touch the Vessels, and
the Air be drawn out of one of these Vessels, and these Vessels thus
prepared be carried out of a cold place into a warm one; the Thermometer
_in vacuo_ will grow warm as much, and almost as soon as the Thermometer
which is not _in vacuo_. And when the Vessels are carried back into the
cold place, the Thermometer _in vacuo_ will grow cold almost as soon as
the other Thermometer. Is not the Heat of the warm Room convey'd through
the _Vacuum_ by the Vibrations of a much subtiler Medium than Air, which
after the Air was drawn out remained in the _Vacuum_? And is not this
Medium the same with that Medium by which Light is refracted and
reflected, and by whose Vibrations Light communicates Heat to Bodies,
and is put into Fits of easy Reflexion and easy Transmission? And do not
the Vibrations of this Medium in hot Bodies contribute to the
intenseness and duration of their H