_MADAM,_
Heat and Cold, according to your _Authors_ opinion, are made by
Dilation and Contraction: for says he,[1] _When the Motion of the
ambient æthereal substance makes the spirits and fluid parts of our
bodies tend outwards, we acknowledg heat, but by the indeavour inwards
of the same spirits and humors we feel cold: so that to cool is to
make the exterior parts of the body endeavour inwards, by a motion
contrary to that of calefaction, by which the internal parts are
called outwards. He therefore that would know the cause of Cold, must
find by what motion the exterior parts of any body endeavour to retire
inwards._ But I desire you to consider, _Madam_, that there be moist
Colds, and dry Heats, as well as dry Colds, and moist Heats; wherefore
all sorts of Cold are not made by the retyring of parts inwards, which
is contraction or attraction; neither are all sorts of Heat made by
parts tending outwards, which is dilation or rarefaction; for a moist
cold is made by dilation, and a dry heat by contraction, as well as a
moist heat is made by dilation, and a dry cold by contraction: But your
_Author_ makes not this difference, but onely a difference between a
dilated heat, and a contracted cold; but because a cold wind is made
by breath blown thorow pinched or contracted lips, and an hot wind by
breath through opened and extended lips, should we judg that all heat
and cold must be made after one manner or way? The contracted mouth
makes Wind as well as the dilated, but yet Wind is not made that way,
as heat and cold; for it may be, that onely the air pressed together
makes wind, or it may be that the corporeal motions in the air may
change air into wind, as they change water into vapour, and vapour
into air; or it may be something else that is invisible and rare, as
air; and there may be several sorts of wind, air, heat, cold, as of
all other Creatures, more then man is capable to know. As for your
_Authors_ opinion concerning the congealing of Water, and how Ice is
made, I will not contradict it, onely I think nature hath an easier
way to effect it, then he describes; Wherefore my opinion is, that it
is done by altering motions; as for example, the corporeal motions
making the figure of water by dilation in a Circle figure, onely alter
from such a dilating circular figure into a contracted square, which
is Ice, or into such a contracted triangle, as is snow: And thus water
and vapour may be changed with ease, without any forcing, pressing,
raking, or the like. The same may be said of hard and bent bodies; and
of restitution, as also of air, thunder and lightning, which are all
done by an easie change of motion, and changing into such or such a
figure is not the motion of Generation, which is to build a new house
with old materials, but onely a Transformation; I say a new house with
old materials; not that I mean there is any new Creation in nature, of
any thing that was not before in nature; for nature is not God, to make
new beings out of nothing, but any thing may be called new, when it is
altered from one figure into another. I add no more at this time, but
rest,
Madam,
_Your faithful Friend_
_and Servant._
[1] _C._ 28. _a._ 1.