| Boyle, Robert New experiments physico-mechanicall, touching the spring of the air and its effects 1660 |
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17
of the Valve, and forcing up of the Suck
er to the top of the Cylinder again, be
driven out into the open Air.
And thus
by the repetition of the motion of the
Sucker upward and downward, and by op
portunely turning the Key, and stopping
the Valve, as occasion requires, more or
less Air may be suck'd out of the Recei
ver, according to the exigency of the Ex
periment, and the intention of him that
makes it.
Your Lordship will, perhaps, think that
I have been unnecessarily prolix in this
first part of my Discourse: But if you
had seen how many unexpected difficul
ties we found to keep out the externall
Air, even for a little while, when some
considerable part of the internal had been
suckt out; You would peradventure al
low, that I might have set down more
circumstances then I have, without set
ting down any, whose knowledge, he that
shall try the Experiment may not have
need of.
Which is so true, that, before we
proceed any further, I cannot think it un
seasonable to advertise Your Lordship,
that there are two chief sorts of Experi
ments, which we design'd in our Engine
to make tryal of: The one, such as may
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