of the
propagation of light through them. Of the _homogeniety_ and _heterogeniety_
of transparent _Mediums_, and what effects they cause on the Rayes of
light, explicated by a Figure: an Examination of the refraction of the Rays
by a plain Surface, which causes Colours. An Examination of the like
effects produced by a spherical Surface: the use that may be made of these
Experiments, for the examination of several _Hypotheses_ of Colours. _Des
Cartes Hypothesis_ examin'd. Some Difficulties taken notice of in it. What
seems most likely to be the cause of colour: that propriety is indeavoured
to be shewn in a Glass ball: that the reflection is not necessary to
produce Colours nor a double refraction: the _Hypothesis_ further examined,
both in the _pellucid Medium_ and in the Eye. The definitions of Colours;
and a further explication and examination of the Proprieties of _laminated_
Bodies; by what means they conduce to the production of Colours._

Observ. 10. Of Metalline Colours.

_That all Colours seem to be caus'd by refraction. An _Hypothesis_
consonant hereunto, explicated by Figures. How several Experiments, of the
sudden changing of Colours by Chymical Liquors may be hereby explicated:
how many wayes such Chymical Liquors may alter the colours of Bodies.
Objections made against this _Hypothesis_ of two colours only, indeavoured
to be answer'd, by several Reasons and Experiments. The reason why some
Colours are capable of being diluted, others not: what those are: that
probably the particles of most metalline Colours are transparent; for this
several Arguments and Observations are recited: how Colours become
incapable of diluting, explicated by a Similitude. An Instrument, by which
one and the same coloured Liquor at once exhibited all the degrees of
colours between the palest yellow and deepest red: as likewise another that
exhibited all varieties of blues: several Experiments try'd with these
Boxes. An Objection drawn from the nature of Painters colours answered:
that diluting and whitening a colour are different operations; as are
deepening and blackening: why some may be diluted by grinding, and some
other by being tempered with Oyl: several Experiments for the explicating
of some former Assertions: why Painters are forced to make use of many
colours: what those colours are: and how mixt. The conclusion, that most
coloured Bodies seem to consist of transparent particles: that all colours
dissoluble in Liquors ar