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THE
PREFACE.
_The following Sheets were not intended to be made publick, but as part
of the Philosophical Transactions. As those Works are printed in the
order of Time they are read; these Observations, communicated to the_
ROYAL SOCIETY _at different Meetings, would, upon that Account, have
been publish'd separate in different Numbers of those Transactions. To
satisfy therefore the Impatience of several learned and very valuable
Friends, to whose Importunities I have neither Will, nor Inclination to
deny any thing in my Power to grant, I caused a few Copies to be
printed, that the whole might be seen together, and then broke up the
Press. This has excited the Curiosity of the Publick, and raised a
Demand for these Experiments much beyond what I had reason to expect. I
therefore found it necessary to send them to the Press a second Time,
lest some of those over-officious Gentlemen, who are always ready on
these Occasions, should do it for me; so that whoever has an
Inclination, may now be made acquainted, by what Means the several
surprizing Phænomena of Electricity have been brought about._
_I chose to lay these Papers before the Publick in the same Dress
wherein they appeared before the very honourable and learned Body, to
whom, as the various Effects of Electricity presented themselves, they
were regularly communicated, and from whom they met with a very
favourable Reception. Many Members of the_ ROYAL SOCIETY, _as well as
several other Persons of great Rank and Quality, have been repeated
Witnesses of the Facts which are here laid before the World;
particularly the present worthy President_, MARTIN FOLKES, Esq; _whose
extensive Abilities and great Knowledge in every Branch of useful
Literature are exceeded only by his Candour and Zeal in promoting
Science. The Advice and Assistance of this Gentleman, whose Friendship I
shall always esteem as one of the greatest Happinesses of my Life, has
been of great Moment in the Prosecution of these Discoveries. I
therefore take this publick Manner of testifying my sincerest
Obligations as well to him, as to Sir_ HANS SLOANE, Bart. _who, although
retired from Business, is nevertheless attentive to whatever tends to
the Advancement of Philosophy. Upon a Report made to him of these
Experiments and Observations, he, as surviving Executor of Sir_ GODFREY
COPLEY, _was pleased to appoint me last Year to receive the annual
Prize-medal of Gold, given by the_ ROYAL SOCIETY _in consequence of Sir_
GODFREY'S _Benefaction. The Honour of being so particularly taken notice
of by Gentlemen of such distinguished Merit, as it cannot but give me
the highest Pleasure, so shall it ever continue to raise in me
Sentiments of the truest Gratitude, and most profound Respect._
_IF it should be asked, to what useful Purposes the Effects of
Electricity can be applied, it may be answered, that we are not as yet
so far advanced in these Discoveries as to render them conducive to the
Service of Mankind. Perfection in any Branch of Philosophy is to be
attained but by slow Gradations. It is our Duty to be still going
forward; the rest we must leave to the Direction of that Providence,
which we know assuredly, has created nothing in vain. But I make no
Scruple to assert, that notwithstanding the great Advances, which have
been made in this part of natural Philosophy within these few Years,
many and great Properties remain still undiscover'd. Future Philosophers
(some perhaps even of the present Age) may deduce from electrical
Experiments, Uses extremely beneficial to Society in general._
_NO present Advantage accrued to those Persons, or to that Age, which
first discover'd the Properties of the Magnet. Many hundreds of Years
intervened, before they were applied to the great Uses of Navigation.
Had these remain'd a secret till now, what other Methods could have been
substituted in their Place, by which we could securely traverse the vast
Ocean? All the Advantages we receive from distant Commerce, we must
still have been Strangers to, but for this fortunate Application of the
magnetical Power. And even the Discoveries thus far had been very
imperfect, without the Knowledge of the Variation of the Compass. But
the present Age, and even this Nation, boasts of a Gentleman[1], who
seems to be entrusted with the magnetical Powers themselves. He makes
artificial Magnets, increases in a few Minutes the Powers of real ones
to a surprizing Degree, changes at Pleasure their Poles, and makes that
newly acquired Polarity, permanent. The World, I hope, will not long be
deprived of the Manner, by which these extraordinary Changes are
produced, which as yet this Gentleman thinks proper to conceal. As
Electricity has some Properties in common with Magnetism, as will be
shewn in the Course of these Observations; some new Lights probably may
be thrown upon both. But to return; admitting even, that no substantial
Advantages could arise from the Inquiries before us, (which, however, we
can by no means grant, upon our considering the Effects we already
perceive of its Operations upon human Bodies) whatever tends to enlarge
the Conceptions of the Mind, and to implant in us still more lofty Ideas
of the Almighty Author of Nature, deserves certainly, independent of
other Considerations, our highest Regard._
_THESE Experiments were all made with Glass Tubes of about two Foot
long; the bore about an Inch in Diameter. But a scrupulous Exactness in
these Proportions is no ways necessary. The thinner and lighter these
Tubes are, the sooner they are excited; though they, 'tis true, don't
retain their Power so long as those, which are more thick and
substantial. But where you intend to communicate the electrical Power,
as fast as you excite it, I should prefer a light Tube; though it ought
never to be less than 1/12 of an Inch thick, because of the Danger of
breaking it by the Friction._
_THE Tube, before it is rubbed, should be always made dry and warm,
which may be done by laying it before the Fire. But I cannot omit
hereupon making one further Remark_; viz. _that Glass Tubes, exactly of
the same Dimensions, made at the same Time, and with the same Materials,
vary considerably with regard to their fitness for electrical Purposes.
Clear and dry Air with some degree of cold is most eligible, though I
have succeeded in the greatest Fogs, but with more Difficulty._
TO
_Martin Folkes_, Esq;
P. R. S.
_SIR_,
THE Society having heard from some of their Correspondents in _Germany_,
that what they call a Vegetable Quintessence had been fired by
Electricity, I take this Opportunity to acquaint you, that on _Friday_
Evening last I succeeded, after having been disappointed in many
Attempts, in setting Spirits of Wine on Fire by that Power. The
preceding Part of the Week had been remarkably warm, and the Air very
dry, than which nothing is more necessary towards the Success of
Electrical Trials; to these I may add, that the Wind was then Easterly
and inclining to freeze. I that Evening used a glass Sphere as well as a
Tube; but I always find myself capable of sending forth much more Fire
from the Tube than from the Sphere, probably from not being sufficiently
used to the last.
I HAD before observ'd, that although[2] Non-electric Bodies made
electrical, lose almost all that Electricity by coming either within or
near the Contact of _Non-electrics_ not made electrical; it happens
otherwise with Regard to _Electrics per se_, when excited by rubbing,
patting, _&c_; because from the rubbed Tube I can sometimes procure five
or six Flashes from different Parts, as though the Tube of two Foot
long, instead of being one continued Cylinder, consisted of five or six
separate Segments of Cylinders, each of which gave out its Electricity
at a different Explosion.
THE Knowledge of this Theorem is of the utmost Consequence towards the
Success of electrical Experiments; inasmuch as you must endeavour by all
possible Means to collect the Whole of this Fire at the same Time.
Professor _Hollman_ seems to have endeavour'd at this and succeeded, by
having a tin Tube, in one End of which he put a great many Threads,
whose Extremities touch'd the Sphere when in Motion, and each Thread
collected a Quantity of electrical Fire, the Whole of which center'd in
the tin Tube, and went off at the other Extremity. Another Thing to be
observ'd, is to endeavour to make the Flashes follow each other so fast,
as that a Second may be visible before the First is extinguish'd. When
you transmit the electrical Fire along a Sword or other Instrument,
whose Point is sharp, it often appears as a Number of disseminated
Sparks, like wet Gunpowder or _Wild-fire_; but if the Instrument has no
Point, you generally perceive a pure bright Flame, like what is vulgarly
call'd the _Blue-ball_, which gives the Appearance of Stars to fired
Rockets.
THE following is the Method I made use of and was happy enough to
succeed in. I suspended a Poker in silk Lines; at the Handle of which I
hung several little Bundles of white Thread, the Extremities of which
were about a Foot at right Angles from the Poker. Among these Threads,
which were all attracted by the rubbed Tube, I excited the greatest
electrical Fire I was capable, whilst an Assistant near the End of the
Poker held in his Hand a Spoon, in which were the warm Spirits. Thus the
Thread communicated the Electricity to the Poker, and the Spirit was
fired at the other End. It must be observ'd in this Experiment, that the
Spoon with the Spirit must not touch the Poker; if it does, the
Electricity without any flashing is communicated to the Spoon, and to
the Assistant in whose Hand it is held, and so is lost in the Floor.
By these Means, I fired several Times not only the ætherial Liquor or
Phlogiston of _Frobenius_ and rectified Spirit of Wine, but even common
proof Spirit. These Experiments, as I before observ'd, were made last
_Friday_ Night, the Air being perfectly dry. _Sunday_ proved wet and
_Monday_ somewhat warm, so that the Air was full of Vapour; Wind
South-West and cloudy. Under these Disadvantages, on _Monday_ Night I
attempted again my Experiments; they succeeded, but with infinitely more
Labour than the preceeding, because of the Unfitness of the Evening for
such Trials. _Your Candour_ will not permit you to think my Minuteness
trivial, with Regard to the Circumstances of the Weather, who know, how
many Things must concur to make these Experiments succeed. I shall wait
with Impatience for a proper Opportunity to have these Experiments
repeated in your Presence, and am, with the utmost Respect,
_Sir, your most obedient,_
_humble Servant_,