ened
again, before it can be brought to a temper, fit for Drills or Penknives.
And I confess _Pyro._ I have taken much pleasure to see the Colours run
along from the parts of the Steel contiguous to the flame, to the end of
the Instrument, and succeed one another so fast, that if a man be not
vigilant, to thrust the Steel into the tallow at the very nick of time, at
which it has attain'd its due Colour, he shall miss of giving his tool the
right temper. But because the flame of a Candle is offensive to my weak
eyes, and because it is apt to either black or sully the contiguous part of
the Steel which is held in it, and thereby hinder the change of Colours
from being so long and clearly discern'd, I have sometimes made this
Experiment by laying the Steel to be tempered upon a heated bar of Iron,
which we finde also to be employ'd by some Artificers in the tempering of
such great Instruments, as are too big to be soon heated sufficiently by
the flame of a Candle. And you may easily satisfie your self _Pyro_: of the
differing hardness and toughness, which is ascribed to Steel temper'd at
different Colours, if you break but some slender wires of Steel so
temper'd, and observe how they differ in brittleness, and if with a file
you also make tryal of their various degrees of hardness.

2 But _Pyrophilus_, I must not at present any further prosecute the
Consideration of the importance of Experiments about Colours, not only
because you will in the following papers finde some instances, that would
here be presented you out of their due place, of the use that may be made
of such Experiments, in discovering in divers bodies, what kind the salt
is, that is predominant in them; but also because a speculative Naturalist
might justly enough allege, that as Light is so pleasing an object, as to
be well worth our looking on, though it discover'd to us nothing but its
self; so modifi'd Light called Colour, were worth our contemplation, though
by understanding its Nature we should be taught nothing else. And however,
I need not make either you or my self excuses for entertaining you on the
subject I am now about to treat of, since the pleasure _Pyro_: takes in
mixing and laying on of Colours, will I presume keep him, and will (I am
sure) keep mee from thinking it troublesome to set down, especially after
the tedious processes (about other matters) wherewith I fear I may have
tyr'd him, some easie, and not unpleasant Experiments relating to