which are the particles which he supposes to constitute the _Pellucid
medium_, But somewhat else, perhaps what we have lately supposed, and shall
by and by further prosecute and explain.

But, First I shall crave leave to propound some other difficulties of his,
notwithstanding exceedingly ingenious _Hypothesis_, which I plainly confess
to me seem such; and those are,

First, if that light be (as is affirmed, _Diopt._ cap. 1. §. 8.) not so
properly a motion, as an action or propension to motion, I cannot conceive
how the eye can come to be sensible of the _verticity_ of a _Globule_,
which is generated in a drop of Rain, perhaps a mile off from it. For that
_Globule_ is not carry'd to the eye according to his formerly recited
Principle; and if not so, I cannot conceive how it can communicate its
_rotation_, or circular motion to the line of the _Globules_ between the
drop and the eye. It cannot be by means of every ones turning the next
before him; for if so, then onely all the _Globules_ that are in the odd
places must be turned the same way with the first, namely, the 3. 5. 7. 9.
11, &c. but all the _Globules_ interposited between them in the even
places; namely, the 2. 4. 6. 8. 10. &c. must be the quite contrary, whence,
according to the _Cartesian Hypothesis_, there must be no distinct colour
generated, but a confusion. Next, since the _Cartesian Globuli_ are
suppos'd (_Principiorum Philosoph._ Part. 3. §. 86.) to be each of them
continually in motion about their centers, I cannot conceive how the eye is
able to distinguish this new generated motion from their former inherent
one, if I may so call that other wherewith they are mov'd or _turbinated_,
from some other cause than refraction. And thirdly, I cannot conceive how
these motions should not happen sometimes to oppose each other, and then,
in stead of a _rotation_, there would be nothing but a direct motion
generated, and consequently no colour. And fourthly, I cannot conceive, how