is a little vers'd in the notions, I have in these, and other Papers hinted
concerning the differences of Salts. And perhaps I might add upon more than
conjecture, that these very notions and some particulars scatteringly
deliver'd in this Treatise, being skilfully put together, may suggest
divers matters (at least,) about Colours, that will not be altogether
Despicable. But those hinted, _Pyrophilus_, I must now leave such as You to
prosecute, having already spent farr more time than I intended to allow my
self in acquainting You with particular Experiments and Observations
concerning the changes of Colour, to which I might have added many more,
but that I hope I may have presented You with a competent number to make
out in some measure what I have at the beginning of this Essay either
propos'd as my Design in this Tract, or deliver'd as my Conjectures
concerning these matters. And it not being my present Designe, as I have
more than once Declar'd, to deliver any Positive Hypothesis or solemn
Theory of Colours, but only to furnish You with some Experiments towards
the framing of such a Theory; I shall add nothing to what I have said
already, but a request that you would not be forward to think I have been
mistaken in any thing I have deliver'd as matter of Fact concerning the
changes of Colours, in case you should not every time you trye it, find it
exactly to succeed. For besides the Contingencies to which we have
elsewhere shewn some other Experiments to be obnoxious, the omission or
variation of a seemingly unconsiderable circumstance, may hinder the
success of an Experiment, wherein no other fault has been committed. Of
which truth I shall only give you that single and almost obvious, but yet
illustrious instance of the Art of Dying Scarlets, for though you should
see every Ingredient that is us'd about it, though I should particularly
inform You of the weight of each, and though you should be present at the
kindling of the fire, and at the increasing and remitting of it, when ever
the degree of Heat is to be alter'd, and though (in a word) you should see
every thing done so particularly that you would scarce harbour the least