frighted, I purposely declin'd in what I writ to him, the setting down any
Number of such Chymicall Experiments, as, by being very elaborate or
tedious, would either require much skill, or exercise his patience. And yet
that this sort of Experiments is exceedingly Numerous, and might more than
a little inrich the History of Colours, those that are vers'd in Chymical
processes, will, I presume, easily allow me.

And (Lastly) for as much as I have occasion more than once in my several
Writings to treat either porposely or incidentally of matters relating to
Colours; I did not, perhaps, conceive my self oblig'd, to deliver in one
Treatise _all_ that I would say concerning that subject.

But to conclude, by summing up what I would say concerning what I _have_
and what I _have not_ done, in the following Papers; I shall not (_on the
one side_) deny, that considering that I pretended not to write an accurate
Treatise of Colours, but an Occasional Essay to acquaint a private friend
with what then occurrd to me of the things I had thought or try'd
concerning them; I might presume I did enough for once, if I did clearly
and faithfully set down, though not _all_ the Experiments I could, yet at
least such a variety of them, that an attentive Reader that shall consider
the Grounds on which they have been made, and the hints that are purposely
(though dispersedly) couched in them, may easily _compound_ them, and
otherwise _vary_ them, so as very much to increase their Number. And yet
(_on the other side_) I am so sensible both of how much I have, either out
of necessity or choice, left undone, and of the fruitfullness of the
subject I have begun to handle; that though I had performed far more then
'tis like many Readers will judge I have, I should yet be very free to let
them apply to my Attempts that of _Seneca_, where having spoken of the
Study of Natures Mysteries, and Particularly of the Cause of Earth-Quakes,
he subjoins.[1] _Nulla res consummata est dum incipit. Nec in hac tantum re